LIBRARY OF^CONGRESS. 

Cha F- Copyright No 



ShellJiX 



UNITED STATES OF AMERICA. 



SE.CJ -^ ^ p/ ' 



SLIDE VALVE GEARS. 



AN EXPLANATION OF THE ACTION AND 

CONSTRUCTION OF PLAIN AND 

CUT-OFF SLIDE VALVES. 



FREDERICK A. HALSEY, 

ASSOCIATE EDITOR OF THE "AMERICAN MACHINIST.-" 

Consulting Engineer of the Rand Drill Company; Member of the American 
Society of Mechanical Engineers. 



^nalgsts fcg tj&e 33tlgram Btagram 



SIXTH EDITION, REVISED AND ENLARGED. 

NEW YORK: 
D. VAN NOSTRAND COMPANY, 

23 Murray and 27 Warren Streets. 
1899. 



28584 



Copyright, 1889, 1898 

BY 

D. Van Nostrand Company. 
TWO COPIES RECEIVED, 



A 







Printed by 

Braun worth, Munn & Barber 

Brooklyn, N. Y., U. S. A 8 



e^jt >v\ &&> • 



(f N 



&> 




TO 

professor 5obn JB. Sweet, 

TO HAVE BEEN WHOSE PUPIL I CONSIDER ONE OF THE 

GREATEST PRIVILEGES OF MY LIFE, 

THIS LITTLE VOLUME IS GRATEFULLY INSCRIBED. 



PREFACE. 



This work has been prepared to meet what the author 
considers a real want. It has been written with the aim 
of making it intelligible to any one who might be will- 
ing to make a serious effort to understand it. High 
authority exists for a mathematical treatment of the 
subject, but with this the author has no sympathy. 
Designing a valve gear is essentially a drawing board 
process, and a mathematical treatment of it is simply 
an uncalled for use of heavy artillery. The graphical 
treatment is therefore adopted throughout. 

Acknowledgment is due to Mr. Hugo Bilgram for 
his courtesy in kindly permitting the use of his valve 
diagram. The author has all due respect for the Zeu- 
ner diagram, but that respect is not incompatible with 
the conviction that Mr. Bilgram's method is a marked 
improvement upon it. Valve diagrams are used for two 
purposes — to analyze existing valve motions and to de- 
sign new ones. The Zeuner diagram fulfils the first pur- 
pose perfectly, but is unsatisfactory when applied to 
the second. The leading data that are given in design- 
ing a valve motion are the point of cut-off, the port open- 
ing, and the lead of the valve (not the lead angle of the 
crank, as is often conveniently assumed). It is the radi- 

iii 



IV PREFACE. 

cal defect of the Zeuner diagram that none of these di- 
mensions can be laid off from known points. The lead 
must be laid off from an unknown point of the centre 
line, and the port opening from an unknown point on 
an unknown line. Finally, through these unknown 
points and the centre of the shaft the valve circle is to 
be drawn from an unknown centre and with an unknown 
radius. Under these circumstances the result sought 
is found only through blind trial. With Mr. Bilgram's 
method all this is changed. The lead is laid off from a 
fixed line, the port opening from a fixed point, and the 
cut-off position of the crank is located. The lap circle 
is then drawn tangent to these lines, and the problem 
is solved. Moreover, the awkward conception of the 
backward rotation of the crank is obviated. Finally, 
these marked advantages are not accompanied by any 
compensating disadvantages whatever. 

Acknowledgment is also due to X\\<t American Ma- 
chinist for the use of a number of engravings originally 
prepared to illustrate some of the author's articles in 
that paper. 

The irregularities due to the connecting rod introduce 
peculiar difficulties into the study of the first principles 
of the slide valve, which difficulties were first overcome 
by the happy expedient of using the slotted cross-head 
instead of the connecting rod in the preliminary study. 
For this, together with many other original and highly 
valuable contributions to the subject, we are indebted 
to Mr. W. S. Auchincloss, who first published them in 
his well-known and standard work entitled Link a?id 
Valve Motions, to which those who wish to prosecute 
their studies beyond the scope of this work are referred. 



PREFACE. V 

The author has gone more fully than is customary 
into the methods of equalizing the various events of 
the stroke. The sections relating to these methods 
will be found more difficult to follow than the others, 
while at the same time they form no necessary part of 
a general treatment of the subject. Those who be- 
gin their studies of valve motions with this book, may 
find these chapters too difficult for the first reading. 
They have, therefore, been marked with a star (*) in the 
Table of Contents and in the body of the book, in order 
that they may be omitted, if desired, in the first reading; 
and it should be understood that the chapters not so 
marked form of themselves a complete connected trea- 
tise, of a more elementary character than the book as a 
whole. 

Philadelphia, Oct. 19, 1889. 



PREFACE TO THE SIXTH EDITION. 



THE chief addition to this edition will be found in 
Part IV, which comprises some articles written for the 
American Machinist and republished here by permis- 
sion of the American Machinist Publishing Co. 

The analysis of the action of the link motion here 
given, while qualitative rather than quantitative, is be- 
lieved to recognize two sources of error in that gear 
for the first time, and to show that the error due to 
the angular vibration of the connecting rod, heretofore 
considered the chief error of the gear, is really of 
minor importance, and, in fact, properly considered, 
is a corrective and not a disturbing factor, since its 
effect is to partially compensate another and much 
larger error. 

Advantage has been taken of the opportunity of- 
fered, to make a few minor changes, the most im- 
portant of which is the extension of the section upon 
Exhaust Lap, with the addition of two full page dia- 
grams to it. The author's observations have shown 
him that much confusion prevails among students re- 
garding this subject, which seemed to justify a more 
detailed treatment of it than that given in previous 
editions. 

The author desires to acknowledge his obligations 
to the Schenectady Locomotive Works for facilities 
afforded for examining their present-day practice in 
link motion construction, without which the study 
here embodied in print would not have been under- 
taken. 



TABLE OF CONTENTS. 



The chapters with an asterisk (*) prefixed may be omitted in the first reading 
without breaking the continuity of the subject. 

PART I. 
The Slide Valve with Fixed Eccentric. 

PAGE 

The Plain Slide Valve, . . . ..... 3 

The Eccentric, 4 

The Scotch Yoke or Slotted Cross-head, ..... 5 

The Primitive Engine, ........ 7 

Defects of the Primitive Engine, 13 

Lap, 15 

Angular Advance, 18 

Lead, 21 

Exhaust Lap, 25 

Backward Rotation, ......... 26 

The Bilgram Diagram, 28 

Laying out the Slide Valve, 38 

* Velocity of the Valve, ........ 39 

Limitations of the Plain Slide Valve, 40 

The Areas of the Ports and Pipes, . . . . . . 42 

The Angular Vibration of the Connecting Rod, . . . 45 

* The Angular Vibration of the Eccentric Rod, . . . * 49 

* Equalized Exhaust, . . ..... 50 

* Equalized Cut-off, . 54 

Setting the Slide Valve, . . . . . . . . 59 

PART //. 
The Slide Valve with Shifting and Swinging Eccentric. 

PAGE 

The Slide Valve at Short Cut-off, 67 

* Equal Lead and Constant Lead, 77 

The Shifting Eccentric, ........ 78 

vii 



via 



TABLE OF CONTENTS. 



The Swinging Eccentric, 

*The Angularity of the Eccentric Rod, 
^Equalized Lead, .....», 
^Equalized Lead and Cut-off, 

PART III. 

The Slide Valve with Independent Cut-off. 

Introductory Remarks, 

The Gonzenbach Valve Gear, 

The Meyer Valve Gear, 

The Buckeye Valve Gear, 

The Straight Line Independent Cut-off Valve Gear, 

The Bilgram Valve Gear, 




80 

85 
89 
95 



101 
102 
109 
116 
120 
122 



PART IV. 

The Slide Valve with Link Motion. 

The Applicability of the Link Motion to Locomotive Conditions 

The Stationary and Shifting Link Motions Compared, 

The Link Motion and Shifting Eccentric Compared, 

The Stationary Link Gives Constant Lead, 

The Shifting Link Gives Variable Lead, 

The Correct Radius of the Link, 

Long and Short Eccentric Rods 

Open and Crossed Rods, 

The Bilgram Diagram, 

The Action of the Link, 

Errors of the Link Motion, 

The Error Due to the Angular Vibration of the Connecting Rod 

The Error Due to the Angular Vibration of the Eccentric Rods 

The Errors Due to the Location of the Eccentric Rod Pins 

Back of the Link Arc, 
The Final Offset, .... 
The Adjustment of the Saddle Stud, 
The Proportions of the Link Motion, 
The Area of the Ports, 
Port Opening and Area of Nozzle, 
Blast Nozzle Areas Compared with Piston and Port Areas 
Smaller Ports Advocated, 
Results from Actual Engines, 
Recent Practice in Valve Setting, . 



133 
137 

138 

l42 

143 
147 
147 
149 

151 
153 

157 
158 
162 

166 
170 
172 

175 
177 
178 

179 
180 
182 
185 



Part I. 

THE SLIDE VALVE WITH FIXED 
ECCENTRIC. 



The Slide Valve with Fixed Eccentric. 



THE PLAIN SLIDE VALVE. 



Fig. I is a sectional view of a plain slide valve and 
its seat, the valve being shown in its central position, 
with the ports completely covered by it. The distance 




Fig. 1 

a, by which the valve extends beyond the steam edge 
of the port, is called the outside lap, steam lap, or more 
usually, simply lap of the valve. The distance b, by 
which it extends beyond the exhaust edge of the port, 
is called the inside lap or exhaust lap.* The exhaust 

* As will be more fully shown later on, valves are sometimes so made 
that the steam is admitted by the inside and exhausted by the outside 
edges. Hence the terms inside and outside lap are somewhat am- 
biguous. The terms steam lap and exhaust lap avoid this ambiguity, 
and are to be preferred. 
3 



4 SLIDE VALVE GEARS. 

lap is always much smaller than the steam lap. It is 
frequently absent, and frequently the exhaust edge of 
the valve does not reach the exhaust edge of the port, 
being made as shown by the dotted lines. In that 
case the distance c is usually called inside clearance, 
though a better name is negative inside or exhaust lap. 
It is sometimes called inside lead or exhaust lead ; but 
these terms should not be applied here, as they have 
properly another definite meaning, which will be ex- 
plained farther on. The measurement for both steam 
and exhaust lap is made for one end of the valve only. 
Thus if a valve is said to have £ inch lap, the meaning 
is that it has that much at each end. 



THE ECCENTRIC. 

The slide valve is usually driven by means of an eccen- 
tric on the crank shaft, and it becomes necessary at the 
outset to obtain a clear conception of the motion which 
the eccentric gives. In brief, the eccentric is a short 
crank with a large crank pin. It is obvious that the 
motion of a cross-head would not be changed by in- 
creasing the size of the crank pin. If a crank pin were 
enlarged until the crank shaft came within the cir- 
cumference of the pin, the result would be an eccen- 
tric. The arm of a crank is the distance from the 
centre of the shaft to the centre of the crank pin, and 
similarly the "throw" of an eccentric is the distance 
from the centre of the shaft to the centre of the eccen- 
tric disc. Usually the centre of the disc is within 
the circumference of the shaft ; but this does not alter 



THE SCOTCH YOKE OR SLOTTED CROSS-HEAD. 5 

the nature of the device, which remains simply a short 
crank with a large crank pin. 



THE SCOTCH YOKE OR SLOTTED CROSS-HEAD. 

The usual method of connecting the cross head to 
the crank pin by means of a connecting rod introduces 
certain distortions and irregularities into the relative 
motions of the piston and crank. These will be more 
fully explained farther on, but it is desirable in the 
first instance to avoid the necessity for considering 
them, as they greatly complicate the subject. This is 
accomplished by considering in the first instance an 
engine having the piston and crank connected by 
means of the device called the Scotch yoke or slotted 
cross-head, since that connection is without the distor- 
tions mentioned.* As has been explained, the eccen- 
tric is essentially a crank ; and it follows that the dis- 
tortions which are introduced by the connecting rod 
into the motions of the piston and crank, are also in- 
troduced by the eccentric rod into the motions of the 
valve and eccentric. The reasons which lead to the 
adoption of the slotted cross-head in place of the con- 
necting rod also require its use in place of the eccen- 
tric rod. An engine fitted with slotted cross-heads is 
illustrated in Figs. 2-1 1. The slotted cross-head will 
be recognized at once, and is too familiar a device to 
need further description. 

*The slotted cross-head is employed here with the permission of 
Mr. W. S. Auchincloss, to whom the thanks of the author are due. 



SLIDE VALVE GEARS. 




THE PRIMITIVE ENGINE. 7 

THE PRIMITIVE ENGINE. 

When illustrating the action of the valve of a steam 
engine, it is essential for clearness that the valve be 
shown on the top of the cylinder. A valve so located 
in an actual engine would require the use of a rock 
shaft to communicate the motion of the eccentric rod 
to the valve rod — a construction which finds use in 
American locomotives. This rock shaft complicates 
the action of the parts, and it is desirable in this pre- 
liminary work to avoid it. To accomplish this the 
unmechanical arrangement of Figs. 2-1 1 is adopted. 

Figs. 2-6 represent the primitive engine with the 
parts in a number of successive positions. The valve 
has no lap on either steam or exhaust side, and the 
eccentric is set at right angles to the crank, and in ad- 
vance of it in the direction of the rotation. The ec- 
centric, being in fact a crank, is represented as such, 
a-nd the valve is driven from it by a slotted cross-head, 
which is secured to the valve stem by the bracket 
shown. In Figs. 3-6 the slotted cross-heads are rep- 
resented by their centre lines only, for greater clearness 
and simplicity. 

Referring to Fig. 2, the crank is on the "centre," 
and the parts are ready to begin movement, the direc* 
tion of rotation being as shown by the arrow. In Fig. 
3 the crank shaft has turned through an angle of forty 
five degrees, carrying the parts to the positions shown* 
Considering Figs. 2 and 3, it is clear that the first move- 
ment of the crank shaft carried the valve to the right, 
and thereby opened port x to steam and y to exhaust. 
Opening port x admitted steam behind the piston to 



SLIDE VALVE GEARS. 





THE PRIMITIVE ENGINE. 



// 



<? 



x ^... 



J 



\ 




IO 



SLIDE VALVE GEARS. 



/}' 



\ 










THE PRIMITIVE ENGINE. II 

drive it forward, and opening y enabled the steam 
which previously filled the space in front of the piston 
to escape to the cavity z y which communicates through 
the exhaust pipe with the atmosphere or condenser, as 
the case maybe. In Fig. 4, the crank shaft has turned 
through an additional angle of forty five degrees, bring- 
ing it at right angles to its initial position. The pis- 
ton is now at the centre of its travel, and the valve at 
its extreme right hand position. As the rotation con- 
tinues, the piston continues to advance ; but the valve 
reverses its motion, and gradually closes its ports, until 
when the crank completes a half revolution, as shown 
in Fig. 5, the valve reaches its middle position at which 
it stood in Fig. 2, with all ports closed. Concinuing 
the motion, the valve is carried to the left, opening 
port^ to steam and x to exhaust, as shown in Fig. 6, 
and the piston is driven back to its original position ; 
and this sequence of operations will obviously continue 
indefinitely. 

With the eccentric located as in the figures, the di- 
rection of rotation must be as described. This will be 
apparent if, starting with Fig. 2, rotation in the opposite 
direction be imagined. The effect of this would be to 
open port x to exhaust and y to steam, thereby effectu- 
ally stopping the rotation in the direction imagined. 
To effect this reverse rotation the eccentric must be 
located diametrically opposite to the position shown in 
the figures.* The student should satisfy himself of 

* This is true with the primitive form of valve only. With valves 
having lap, as actually used, the eccentric position for reverse rota- 
tion is not diametrical iy opposite from the position required for for- 
ward rotation. This subject will be referred to again. 



12 



SLIDE VALVE GEARS. 







DEFECTS OF THE PRIMITIVE ENGINE. 1 3 

the correctness of this fact by supposing the eccentric 
so located, and then following the motion through a 
revolution. 

Throughout this book, whether shown or not, it will 
be understood that the cylinder is located as in the 
figures already explained, i.e., to the left of the shaft; 
and unless otherwise specified, that the direction of 
rotation is the same as in these figures, i.e., " over." 



DEFECTS OF THE PRIMITIVE ENGINE. 

With the construction of Figs. 2-6 the opening and 
closing of the ports are coincident with the passing of 
the centre by the crank. Economy of steam and suc- 
cessful running require that the following changes be 
made in this distribution of the steam : 

I. The opening of the steam port or "admission" 
should occur slightly before the crank reaches the cen- 
tre.* In a general sense this is called giving the valve 
steam lead or simply lead. In a more strict sense, that 
term means the width of opening in fractions of an 
inch which the valve has given to the steam port at the 
instant the crank passes the centre. 

II. The closing of the steam port or " cut-off " should 
occur a good deal before the crank passes the centre. 

III. The opening of the exhaust port or "release," 

* Of late years a difference in practice has arisen in this respect. 
Some makers now set their valves to open the port just as the crank 
passes the centre, and in some cases the admission is delayed until 
after that event. The statement in the text, however, represents 
general practice. This subject will be referred to again farther on. 



14 



SLIDE VALVE GEARS. 



«? 



^ pi 





LAP. IS 

and its closing or " compression," should occur earlier 
than the opening of the steam port, but not so early as 
its closing. As the width of port opening to steam as 
the crank passes the centre is called steam lead, so the 
width of opening to the exhaust at the same instant is 
called exhaust lead or inside lead (compare page 4). 

These changes in the steam distribution are brought 
about by two changes in the valve gear : (I.) The valve 
is given lap, and (II.) The eccentric is advanced on the 
shaft ahead of the position given. 



LAP. 



Fig. 7 is a reproduction of Fig. 2, with the addition 
of outside or steam lap to the valve. There is no 
change in the exhaust side of the valve nor in the 
angular position of the eccentric, and it is obvious that 
the ports will be opened and closed to the exhaust as 
the crank passes the centre exactly as before ; but the 
port x will not be opened to steam until the valve has 
been carried to the right an amount equal to its lap. 

This will happen as shown in Fig. 8, when the shaft 
has turned through an angle def, such that df, or what 
is the same thing, eg, is equal to the lap. This angle 
def is called the lap angle. The valve opens port x to 
steam when the edge of the valve passes the edge of 
the port going to the right, and it closes it when the 
edge of the valve passes the edge of the port going to 
the left. The position of the valve is the same at clos- 
ing as at opening, the only difference between the two 
acts being in the direction of the valve's motion; con- 



i6 



SLIDE VALVE GEARS. 




LAP. 



17 




1 8 SLIDE VALVE GEARS. 

sequently the port must close with the eccentric at h, 
vertically below/*, as shown in Fig. 9. From this, two 
important and fundamental facts can be learned : 

I. During the time that steam was being admitted 
the eccentric (and with it the shaft and crank) turned 
through the angle feh. Now feh is equal to a semi- 
circle less def and less hei, that is, a semicircle less twice 
the lap angle, and this is the first result of the addition 
of lap to the steam side of the valve. During the 
admission of steam the crank turns through an angle 
equal to a semicircle less twice the lap angle. 

II. In the case of the primitive valve of Figs. 2-6, the 
port began to open with the eccentric in the position of 
Fig. 2. It attained its greatest opening in the position 
of Fig. 4, and the maximum width of port opening was 
equal to the throw of the eccentric. With the valve of 
Figs. 7-9, however, the port does not begin to open 
until the eccentric reaches the point/, and the remain- 
ing travel gk only is available as port opening. This 
width of opening,^, is equal to ek less eg, that is, to 
the throw of the eccentric less the lap of the valve ; and 
it follows at once that if a valve with lap is to give the 
same port opening as another Avithout lap, the eccentric 
throw of the former must exceed that of the latter, and 
the greater the lap the greater must be the throw. 



ANGULAR ADVANCE. 

The last section has shown how, by the addition of 
lap, the period of port opening may be shortened as 
desired. While, however, the method of regulating 



ANGULAR ADVANCE. 1 9 

the length of period of port opening was pointed out, 
nothing was said about properly timing the opening 
or closing of a valve having lap with reference to the 
position of the piston, and in point of fact in Fig. 8 
the port opening to steam occurred long after the 
crank had passed the centre. The correct timing of 
the events of the stroke, and especially of the admis- 
sion of steam, is obtained by advancing the eccentric 
around the shaft from the position thus far shown. 
In order to give admission to the steam at the instant 
the crank passes the centre, it is necessary to first 
locate the crank on the centre, then to advance the 
eccentric around the shaft such an amount as to 
draw the valve to the right a distance equal to the 
steam lap, and finally to secure the eccentric in that 
position. Such a setting of the eccentric is shown in 
Fig. 10, in which the eccentric has been turned forward 
until the distance df ox its equal, eg, is equal to the lap. 
Such advance of the eccentric on the shaft is called the 
angular advance or the advance angle of the eccentric ; 
and if the admission is to occur with the crank on the 
centre, as in this instance, the advance angle of Fig. 10 
is equal to the lap angle of Fig. 8. Having secured a 
proper admission to the steam, it is proper to inquire 
next into the effect which this change in the angular 
position of the eccentric has had on the other events of 
the stroke. It is sufficiently obvious that turning the 
eccentric forward a given angle would simply cause 
each event to occur that much earlier in the rotation 
of the crank. After steam lap had been added, and 
before the advance of the eccentric, the cut-off occurred 
with the crank lacking one lap angle of having reached 



20 



SLIDE VALVE GEARS. 






v 



:s-r 



_ 4^ _. 



V8 



./ 




LEAD. 21 

the centre (see Fig. 9). Advancing the eccentric one 
lap angle will cause cut-off to occur one lap angle earlier 
still, or with the crank lacking two lap angles of having 
reached the centre. Before the advance of the eccen- 
tric, the opening and closing of the ports to the exhaust 
occurred as the crank passed the centre (see Figs. 5 and 
7). Advancing the eccentric one lap angle will there- 
fore cause both release and cornpresssion to occur with 
the crank lacking one lap angle of having reached the 
centre. 

Summarizing then, the valve has had steam lap 
added to it, and the eccentric has been advanced by 
an angle equal to the lap angle, and the resulting steam 
distribution is as follows : Admission occurs as the crank 
passes the centre ; cut-off occurs two lap angles before 
the centre ; and release and compression occur one lap 
angle before the centre. 

Throughout this book the advance angle will be 
designated on the diagrams by the letter S (delta). 



LEAD. 

It was explained on page 13 that the admission of 
steam should take place slightly before the crank 
reached the centre, and that such early admission was 
called lead. In the last section, for the sake of sim- 
plicity, the admission was supposed to occur as the 
crank passed the centre. In other words, the lead was 
made zero. It now becomes in order to examine the 
method for the introduction of lead, and the changes 
in the other events of the stroke which follow. In Fig. 



22 



SLIDE VALVE GEARS. 




£ 



LEAD, 23 

10 the eccentric was advanced to cause admission to 
occur on the centre. If it is proposed to give the valve 
lead, the eccentric must be advanced still further, so as 
to draw the valve to the right an additional amount 
equal to the lead desired. In Fig. 1 1 this additional 
advance has been made, the eccentric having been 
moved from /of Fig. 10 (reproduced in Fig. 1 1) to /. 
The angle fel is called the lead angle, and it follows that 
in all cases the angular advance is equal to the lap angle 
plus the lead angle. If the lead is zero, then, as be- 
fore found, the angular advance is equal to the lap an- 
gle. If in Fig. 1 1 the crank shaft be turned backward, 
the valve will close the port when the eccentric reaches 
point/* and the crank stands at m, the angle nem being 
equal to the angle fel. In other words, the lead angle 
is equal to the angular distance which the crank lacks 
of having reached the centre when admission occurs. 

It was found on page 19 that advancing the eccentric 
on the shaft a given angle advanced all the events of 
the stroke correspondingly, and the resulting distribu- 
tion of steam with no lead was summarized on page 21. 
If now the valve have lead so that the angular ad- 
vance be greater than the lap angle, the steam dis- 
tribution given on page 21 is changed as follows: 

Admission occurs with the crank lacking the lead 
angle of having reached the centre. 

Cut-off occurs with the crank lacking two lap angles 
and one lead angle of having reached the centre. 

Release and compression occur with the crank lack 
ing one lap angle and one lead angle of having reached 
the centre. 

An application of the above principles is all that is 



24 



SLIDE VALVE GEARS, 



necessary for the analysis of the steam side of any exist- 
ing plain slide valve, as will be seen from the following 
example : 

An eccentric has a throw of if", the valve has one- 



e m 




Fig. 12 

inch steam lap, no exhaust lap, and the eccentric is set 
to givey^" lead. Required the greatest port opening, 
and the crank positions for admission, cut-off, release, 
and compression. 

In Fig. 12 strike the circle with a radius equal to the 



i 



EXHAUST LAP, 2$ 

throw of the eccentric, and lay off Oa equal to the lap 
of the valve and a b equal to the lead. Erect perpen- 
diculars from points a, b, giving points c, d. Now eOc is 
the lap angle, cOd is the lead angle, and eOd is the an- 
gular advance. Lay off fg equal to cd, giving Og the 
crank position for admission. Make hi equal to twice ec 
plus cd, giving the crank position Oi for cut-off. Make 
kh equal to ec plus cd, giving Ok the crank position for 
release and compression. Finally, ah is the greatest 
steam port opening. 

The student should familiarize himself with the prin- 
ciples thus far treated, by the solution of a variety of 
problems similar to the following : 

Problem I. Eccentric throw if, lap f, lead -j^-. Re- 
quired crank positions for lead, cut-off, compression and 
release, and port opening to steam. 

Problem II. Eccentric throw if, lap \\, lead ^\. Re- 
quired as before. 



EXHAUST LAP. 

The action of exhaust lap upon release and com- 
pression is precisely the same as that of steam lap 
upon admission and cut-off. The proportions existing 
between exhaust lap and angular advance are, however, 
quite different from those between steam lap and an- 
gular advance — a fact which in a measure obscures the 
really identical action of lap on the two edges of the 
valve, and renders some special attention to exhaust lap 
desirable. The sum of the steam lap and lead angles 



25# 



SLIDE VALVE GEARS. 



//" 






X 



— i ~i — 1 — 



! 



z r--— * & j 




EXHAUST LAP. 2^b 

has already been shown to be equal to the angle of 
advance, and in precisely the same way the sum of the 
exhaust lap and lead angles is also equal to the advance 
angle. Considering the steam side, however, the lead 
angle is but a small part of the advance angle — the lap 
a.igle being nearly equal to the advance angle. The 
exhaust lap is always much smaller than the steam lap, 
the exhaust lap angle is correspondingly small and the 
exhaust lead angle correspondingly large — being in fact 
the larger of the two. 

Fig. \2a shows in full lines the parts in the same 
position as in Fig. 7, with no angular advance to the 
eccentric, but with the addition of inside lap to the 
valve. It will be apparent that port y will be opened 
to exhaust when the valve has moved to the right an 
amount equal to the exhaust lap, which will happen 
when the shaft and eccentric have turned to the posi- 
tion shown by the dotted lines, such that the horizon- 
tal distance do is equal to the exhaust lap, and the 
port will close again when the eccentric has turned 
through the angle oep to the point p vertically below 
0. The angle deo is obviously the exhaust lap angle, 
and the angle oep, during which the port remains open 
to the exhaust, is equal to a semicircle less twice the 
exhaust lap angle, precisely as with the steam side of 
the valve. 

In Fig. \2b the eccentric is shown turned forward 
on the shaft to give steam lead as in Fig. II, point 
being reproduced from Fig. \2a. It is evident that 
turning the eccentric from to /drew the valve to the 
right and gave exhaust lead, the angle oel being the 
exhaust lead angle, as fel of Fig. 1 1 is the steam lead 



2$C 



SLIDE VALVE GEARS. 



/ 



^ v 



\ x 

\ 8 
I 3> 



\ 



\ 



/ 8 







I? 



EXHA US T LAP. 2^d 

angle. It will thus be seen that the action of exhaust 
lap does not differ from that of steam lap, except in 
degree, and a moment's reflection will show that the 
extreme opening of the port to exhaust is equal to the 
throw of the eccentric less the exhaust lap precisely 
analogous to the steam port opening as stated on 
page 1 8. 

Furthermore, companion statements relating to ex- 
haust opening and closure could be made to those on 
page 23, relating to steam lead and cut-off, but these 
points for a valve having exhaust lap are more usually 
stated with reference to what they would be if the 
valve had no such lap. 

Reference to Fig. \2a will show that the effect of 
exhaust lap is to delay the opening and hasten the 
closing of the port, and in each case by an angle of 
rotation of the shaft equal to an exhaust lap angle ; 
that is, release occurs a lap angle later and compres- 
sion a lap angle earlier than they would if the valve 
had no exhaust lap. 

As stated on page 4, exhaust lap is frequently ab- 
sent and even negative (in which latter case it is often, 
though without much significance, called inside clear- 
ance). The effects of negative exhaust lap are of 
course the opposite of those of positive lap. That is, 
negative lap hastens the opening and delays the clos- 
ing of the port, and, as with positive lap, in each case 
by an angle of rotation of the crank equal to the (neg- 
ative) lap angle, and while with positive lap the period 
or port opening is equal to a semicircle less two lap 
angles, with negative lap it is equal to a semicircle 
plus two lap angles. 



26 



SLIDE VALVE GEARS. 



Negative inside lap also acts to increase the max- 
imum port opening beyond the amount due to a valve 
made " line and line," the opening being equal to the 
throw of the eccentric plus the numerical value of the 
negative lap. 



BACKWARD ROTATION. 



It was explained on page 1 1 that with a primitive 
valve the eccentric location for rotation in the reverse 
direction would be diametrically opposite that shown 
in Figs. 2-6. For a valve having lap, the position for 
reverse rotation is found by laying off the advance 
angle in the direction of the proposed rotation from the 
position for a primitive valve. The effect of a rock 
shaft in the valve motion (for an example of which see 
any American locomotive) is to reverse the motion of 
the valve as compared with the eccentric, and hence to 
require a location of the eccentric which will provide 
for this reversal. The position of the eccentric for 
either direction of rotation, and with or without a rocker, 
may be located from the following facts : 

I. Without a rocker the eccentric for a primitive 
valve is 90 in advance of the crank in the direction 
of the rotation. With a rocker the eccentric is behind 
the crank. 

II. The advance angle is laid off in all cases in the 
direction of the rotation from the position for a primi- 
tive valve. 

One qualification should be added to the above, as 
follows ; In all the cases thus far shown, the location of 



BACKWARD ROTATION. 2J 

the eccentric for the primitive valve is as stated at right 
angles to the crank. In certain cases, owing to the 
character of the connections between the eccentric and 
valve, this is not true. For an example see Figs. 58 
and 59. In cases of this kind the location of the ec- 
centric can be found as follows : Carry the centre of 
the eccentric strap to the centre of the crank shaft. 
Through the centre of the shaft draw a line perpen- 
dicular to the location of the eccentric rod thus found. 
This perpendicular gives the location of the eccentric 
for the primitive valve, and the angular advance is to 
be laid off from it in the direction of the rotation. 



28 



SLIDE VALVE GEARS. 



THE BILGRAM DIAGRAM. 



Any existing slide valve can be analyzed by the 
methods that have been followed in explaining the 
action of the valve, and new valves could be designed 
by a tentative application of the same methods. Such 
a plan of procedure, however, would be exceedingly 
tedious, and much ingenuity has been expended in de- 
vising briefer and better methods. Of these, by far 
the best is the diagram devised by Mr. Hugo Bilgram, 
and explained below. The chief office of such a dia- 
gram is to show briefly and accurately the position of 
the valve for any and every position of the crank. 

A 





Fig. 13 



The demonstration of the Bilgram diagram depends 
upon the following theorem of geometry: In Fig. 13 
let ABC and abc be two triangles, such that any two 
of their angles, as those at A, C and a, c, and any one 
side, as BC and be, are respectively equal. Then this 
theorem asserts that all of the other parts of the tri- 
angles are equal, i.e., angle B to b, side AC to ac, and 
side AB to ab. 

In Fig. 14 let A be the dead-point location of the 
crank, and B be the corresponding position of the ec- 



THE BILGRAM DIAGRAM. 



2 9 



centric centre, 8 being the angle of advance. It is 
obvious enough that the valve is now located a dis- 
tance Bb (equal to the sum of the lap and lead) to the 
right of its middle position. Imagine the crank to 
turn through the angle a to a new position A'. The 
eccentric will turn through an equal angle a to its new 




Fig- U 



position B\ and the valve will then be located a dis- 
tance B'V to the right of its middle position. Lay 
off the angle 8 upward from OX, and thus locate a 
fixed point, Q. From Q drop Qq perpendicular to the 
new crank position extended. There are thus formed 
two triangles, B'b'O and QqO, and in them B'O equals 



30 SLIDE VALVE GEARS. 

Q0< since both are radii of the same circle. Angles 
B'b'O, QqO are equal, because both are right angles; 
and finally, angle B 'Ob' equals QOq, since each is equal 
to 8 plus a. The two triangles have thus two angles 
and a side of one, respectively equal to two angles and 
a side of the other, and it follows that the triangles are 
equal in all their parts, and hence Qq equals B'b '. B'V 
is the distance which the valve has travelled from its 
central position for crank position A ', and it hence 
follows that Qq likewise equals that distance. The 
same demonstration can be made for any other crank 
position as well as for A'., and the following general 
fact is thus established : Lay off the advance angle 
above the centre line, and thus locate the fixed point 
Q. Draw any crank position desired, and extend it if 
necessary. From the fixed point Q drop a perpendic- 
ular to the crank line, and the length of the perpendic- 
ular will be equal to the distance of the valve from its 
central position for the crank position taken. For ro- 
tation in the reverse direction, points B and Q would fall 
below instead of above the centre line. 

The length of the perpendicular Qq gives the dis- 
tance of the valve from its central position, but it does 
not of itself show whether the valve is located to the 
right or to the left of its middle position. That fact 
will be determined instinctively after a little practice 
in the use of the diagram ; but if desired it can be 
determined by the following consideration : Referring 
to Fig. 14, that side of the crank and of its imaginary 
extension facing the space toward which the crank is 
revolving may be called the face side of the crank, and 
the opposite side may be called the rear side. If the 



THE BILGRAM DIAGRAM. 3 1 

perpendicular Qq falls upon the face side of the crank, 
the valve is to the right of its middle position ; if the 
perpendicular falls upon the rear side, the valve is to 
the left of its middle position.* As has been explained, 
the greatest port opening is equal to the throw of the 
eccentric OQ y Fig. 14, less the lap ; and it is also true 
that for any position of the crank, the port opening 
which exists at that position is equal to the displace- 
ment of the valve from its central position less the lap, 
i.e., to the value of Qq for that position, less the lap. In 
other words, if for any crank position the value of Qq 
be found, and from it the steam lap be taken, the result 
will be the distance which the steam port stands open for 
that crank position. If, on the other hand, the exhaust 
lap be taken from it, the result will be the distance which 
the exhaust port stands open. This subtraction can 
be conveniently made by striking tw r o circles Z, / from 
Q as a centre, and with radii equal to the steam and 
exhaust laps respectively, as is done in Fig. 15. In 
case the inside lap is negative, it of course increases 
instead of decreases the port opening to exhaust. 
Throughout this book, positive lap will be shown by 
full circles, and negative lap by dotted circles. 

Starting with the position A, Fig. 15, the length of 
the perpendicular which locates the valve is Qq, and the 
width of opening of the port to steam is aq ; A being 
the dead-point position of the crank, aq is the lead of 
the valve. Similarly, bq is the exhaust lead. In Fig. 16 
the valve is showm in position for crank position A. 



* This takes it for granted, as explained on page 13, that the posi- 
tion of the cylinder is to the left of the shaft. 



32 



SLIDE VALVE GEARS. 



The opening of the port c to steam is equal to aq of 
Fig. 15, and the opening of port d to exhaust is equal 
to bq. Similarly, the displacement e of the valve from 
its centre is equal to Qq* As the crank revolves, Qq 
gradually lengthens until the crank reaches position B 
perpendicular to OQ, when Qq becomes QO, which is its 




greatest value. The valve now stands at its extreme 
right hand position as shown in Fig. 17, the ports being 
open to their greatest amount — the steam port by a 



* It will be understood that the distances stated as equal are not so 
shown in the cuts, as they are necessarily drawn to different scales. 



THE B1LGRAM DIAGRAM. 



33 



width a f 0, and the exhaust port b r 0. Passing B, the 
valve returns towards its central position, and at C the 




Fig. 16 

displacement has been reduced to equality with the 
steam lap. The port c is therefore closed to steam, and 




cut-off takes place as shown in Fig. 18. At D, port d 
is closed to the exhaust, Fig. 19, and compression be- 




Fig. 18 

gins. At F, port c is opened to exhaust, Fig. 20, and 
release occurs. At G the valve is ready to open port 
d for the return stroke, Fig. 21 ; and at H the valve has 



34 



SLIDE VALVE GEARS. 



opened port d by the amount of the lead. The posi- 
tions of the crank for the return stroke are readily found 




Fig. 19 

by extending the crank lines beyond the centre. Thus 
/ is the lead position, K the release, M the compression, 




Fig. 20 

and iVthe cut-off. Had there been no exhaust lap, re- 
lease and compression would have occurred simultane- 




Fig. 21 

ously at E ; and had the exhaust lap been negative, re- 
lease and compression would have exchanged places, 
and the maximum opening to exhaust would have been 
Ob". 



THE BILGRAM DIAGRAM. 35 

Consideration of this diagram will recall and enforce 
the essential effect of lap, as stated on page 18 ; i.e., to 
shorten the period during which the port is open. Thus 
with steam lap the steam port is open when the crank 
is moving from /to Cand from G to N, and with exhaust 
lap the exhaust port is open from K to D and from F 
to M. With negative inside lap, on the other hand, 
the port is open during more than half a revolution, 
i.e., from M to F. 

The principles laid down should be fixed in the mind 
by the solution of practical problems similar to the 
following : 

Problem III. Throw of eccentric 2", steam lap ij, 
exhaust lap £, lead -§-. Required port opening and 
points of cut-off, release, and compression. 

Problem IV. Travel of valve 3", steam lap -J, nega- 
tive exhaust lap y 3 ^, lead f. Required as in the last 
problem. 

This diagram is of use not only in analyzing existing 
valve motions as in the preceding problems, but also in 
designing new ones to meet required conditions. The 
method of using it for this purpose is best shown by an 
illustrative example, as follows : 

The valve for a certain engine is to have a steam- 
port opening of •§-", a lead of y 1 ^ ; is to cut off the steam 
at f of the stroke, and open the exhaust at 95 per cent 
of the stroke. Required the inside and outside lap, the 
throw and advance angle of the eccentric, and the point 
of exhaust closure. 

In Fig. 22 make AB equal to the length of the stroke, 
using a scale of three inches to the foot. Make Aa 



36 



SLIDE VALVE GEARS. 



equal f of AB, and Ad equal .95 of AB. Draw the 
semicircle A'a'b' B' to represent the path of the crank, 
and project to it the points a, b. Draw Oct! and 0b\ 
which are the crank positions for cut-off and release. 
Draw cd such that de is equal to the lead opening, ^ 




Fig. 22 



inch; and strike the arc fg with radius equal to the 
port opening. Find by trial the centre and radius of 
the steam lap circle such that it shall be tangent to 0a\ 
cd, and fg. From the same centre strike the exhaust 
lap circle tangent to 0b\ Draw Oh' tangent to the ex- 
haust lap circle and project ti to the stroke line, giving k. 



THE BILGRAM DIAGRAM. 



37 



Measuring the diagram, the results sought are, outside 
lap ySg- inch, inside lap \ inch, throw of eccentric i-^- 
inch, advance-angle iOB\ point of exhaust closure h, 
which is 90 per cent of the stroke. It may be observed 
further, that the exhaust port opening is Ok ; in this 




case and in all others this is more than sufficient for 
the purpose, and hence no particular care is necessary 
in relation to it. 

An interesting and profitable exercise in this connec- 
tion is to make a diagram showing by a continuous line 
the varying width of port opening throughout the 
stroke. This is illustrated in Fig. 23, in which the con- 
tinuous base line represents the stroke of the piston of 
Fig. 22 divided into tenths. At each division a per- 
pendicular is erected, and on this perpendicular is laid 
off the opening of the ports to steam and exhaust for 
that position of the piston — this opening being obtained 
from Fig. 22. Through the points thus found the 



38 SLIDE VALVE GEARS. 

curved lines are drawn — the upper one for the exhaust 
port and the lower one for the steam port. The cross- 
ing of the base line by the curved lines shows the points 
of cutting off and compression, respectively; and the 
extension of the curved lines below the base line shows 
the distances by which the edges of the valve have 
closed the ports. This diagram shows at a glance how 
gradual is the cutting off of the steam. Such diagrams 
are exceedingly useful in connection with the study of 
independent cut-off valves, many of which will not give 
flattering results when subjected to this analysis. 

LAYING OUT THE SLIDE VALVE. 

The diagram Fig. 22 gives all the dimensions neces- 
sary for laying out its valve, except the width of the ex- 
haust cavity, and that is determined at once by draw- 
ing the valve and its seat w 7 ith the valve at one extreme 
of its travel, that is, in the position already shown in 
Fig. 17. Referring to Fig. 1, it is clear that the width 
of the acting face of the valve is equal to the outside 
lap plus the width of the port plus the inside lap. In 
order to determine all the dimensions of the valve face 
and seat proceed as follows : Lay down the width of 
the left hand port (rules for which will be given farther 
on) and the width of the bridge (usually made equal to 
the thickness of the cylinder). On these locate the 
acting face of the valve with the port open to steam to 
the greatest amount intended. From the exhaust 
edge of the acting face lay off the distance/, Fig. 17, to 
equal or slightly exceed the width of the port, thus com- 
pletely determining the exhaust cavity in the cylinder. 



VELOCITY OF THE VALVE. 39 

From the right hand edge of this cavity the remaining 
bridge and port are to be laid off the same as the 
left hand side. The valve seat being completed, and 
the steam and exhaust laps being known, it is easy to 
complete the drawing of the valve. The proper deter- 
mination of the distance/*, Fig. 17, as above, is all that 
need be considered in designing the exhaust cavity in 
the cylinder. If this cavity be made too narrow, it will 
cramp the exhaust ; if too wide, it will add unnecessari- 
ly to the size of the valve and to the steam pressure 
upon it, and hence to the friction and wear and tear on 
all the valve gear. Further than this, the size of the 
exhaust cavity has no influence on the valve motion. 

It will be observed that in the valve diagram Fig. 22. 
the lines for the piston and crank circle are drawn to a 
reduced scale, but the lines for the valve and eccentric 
are full size. The reduced scale for the crank dimen- 
sions is for convenience. The valve dimensions should 
always be made full size. 

* VELOCITY OF THE VALVE. 

Referring to Fig. 14, it is obvious that the valve 
will move with its greatest velocity when the eccentric 
is at P. At this point its velocity may be represented 
by the eccentric throw OP. At any other position of the 
eccentric as i?, the valve will move with a velocity pro- 
portional to the leverage with which the eccentric acts 
upon it, that is, Ob. Similarly at B' the velocity of the 
valve will be represented by Ob'. In the original dem- 
onstration of this diagram it was shown that the tri- 
angles B'b ' and QqO are equal in all their parts. It 



40 SLIDE VALVE GEARS. 

hence follows that Oq equals Ob\ In other words, if a 
perpendicular be drawn from the point Q to any crank 
line, the distance from the centre of the shaft to the 
foot of that perpendicular will represent the velocity 
with which the valve is moving with the crank in that 
position. Quick closure of the port in cutting off steam 
is considered a merit in a valve motion, and this prop- 
erty of the Bilgram diagram furnishes a ready means 
of comparing the merits of different valve gears in this 
respect. In Fig. 15 the perpendicular Qc will deter- 
mine the distance Oc, which represents the velocity 
with which the valve is moving at the instant of 
cutting off. 

LIMITATIONS OF THE PLAIN SLIDE VALVE. 

Careful study of the Bilgram diagram will explain 
the features of the common slide valve which have usu- 
ally been considered to limit its application to cases 
where a comparatively late cut-off was to be employed. 
Thus, in the example of Fig. 22, let the given condi- 
tions be the same, except that cut-off is to be at half 
stroke instead of three quarters, and let there be no 
inside lap. The results are shown in Fig. 24, where 
it will be seen that the throw has increased to two 
inches and the steam lap to one and three eighths 
inches, while the common point of compression and re- 
lease has gone back to bh — 85 per cent of the stroke. 
At still earlier points of cut-off these features become 
still more marked, the travel of the valve rapidly in- 
creasing and the release and compression becoming 
more and more premature. The increased lap and 
travel increase directly the size and duty which the 



LIMITATIONS OF THE PLAIN SLIDE VALVE. 4 1 

parts have to perform. Further, as will be seen by re- 
ferring to the section on laying out the slide valve, 
and to Fig. 17, they increase the size of the exhaust 
cavity, and so add to the size of the valve and to the 
steam pressure upon it. The release can be made later 




Fig, 24 



by the addition of exhaust lap, but this involves a still 
earlier compression. From these considerations it has 
been generally held and taught that the plain slide 
valve could not be profitably employed for cut-offs 
shorter than one half or five eighths stroke. The 



42 SLIDE VALVE GEARS. 

methods which have been adopted to overcome the 
above difficulties will form the subject of a later chapter, 



THE AREAS OF THE PORTS AND PIPES. 

It will be seen from the foregoing that the width of 
port opening is an essential factor in the design of a 
valve motion. The exact meaning of the term port 
opening in this connection should be clearly under- 
stood. By that term is to be understood the extreme 
distance of the steam edge of the valve from the steam 
edge of the port. This distance may, and often does, 
exceed the width of the port — that is, the valve may 
have over-travel to secure certain real or fancied advan- 
tages. In engines with fixed eccentric, which are now 
under consideration, the only benefit of such over-travel 
is to increase the sharpness of the cutting off. This, in 
the author's opinion, is not worth its cost, and hence he 
does not practise nor recommend it. In locomotives 
and shifting eccentric engines the travel of the valve is 
shortened at the early cut offs, and in such engines, in 
order to secure sufficient port opening at the early cut- 
offs, it is proper and necessary to give over-travel at the 
late ones. 

It is clear that the area of the port opening should 
have a proper relation to the size and speed of the en- 
gine. It will be furthermore clear without extended 
explanation, that in engines having separate admission 
and exhaust ports (for example, the Corliss) the exhaust 
passage should have a greater area than the admission 
passage. In engines using the same passage for both 
purposes, to which this book relates, that passage 
should be proportioned to meet the requirements of 



THE AREAS OF THE PORTS AND PIPES. 



43 



the exhaust, and then, if desired, it need not be opened 
to steam any wider than is necessary for its use as a 
steam port. 

In determining the area of a pipe or passage it is 
treated as though the velocity of the steam through it 
were equal to the velocity of the piston multiplied by 
the ratio of the area of the piston to the area of the 
port or pipe. Of course, owing to the elasticity of 
the steam, the varying velocity of the piston and the 
fact that the port is not constantly opened to its full 
width, this is not true. The rules should however be 
regarded as purely comparative between engines in 
which these factors have substantially the same values 
and hence may be ignored. 

As the result of experience and experiments, the 
proper velocities of the steam through the various pas- 
sageways on the above basis are as follows : 

Through the steam pipe 8000 feet per minute. 

Through the exhaust port 6000 feet per minute. 

Through the exhaust pipe 4000 feet per minute. 

For free admission of steam the port should be opened 
three fourths of its width. From the above data the 
following table is constructed for convenient use : 



Piston Speed, 
Feet per Minute. 


Diameter of Steam 


Diameter of Exhaust 


Area of Exhaust 


Pipe (Diameter of 
Piston = 1). 


Pipe (Diameter 
of Piston = 1). 


Passage (Area ot 
Piston = 1). 


200 


.158 


.223 


.033 


250 


.176 


.248 


.042 


300 


.194 


.272 


.050 


350 


.209 


.294 


.058 


400 


.224 


.314 


.067 


450 


.237 


•333 


.075 


t;oo 


.250 


• 353 


.083 


55o 


.260 


.368 


.092 


600 


. .274 


.385 


. IOO 



44 SLIDE VALVE GEARS. 

The table determines the diameters of the steam 
and exhaust pipes at once, but it gives the area only 
of the port, leaving its length and breadth to be de- 
termined by the designer. The practice in this par. 
ticular is very diverse. In shifting eccentric automa- 
tic engines, which form the subject of Part II, and in 
which every expedient must be employed to secure 
sufficient port opening, the length of the ports is often 
made to equal or even exceed the diameter of the cyl- 
inder; but in plain slide valve engines of the usual type, 
a length of about three quarters the cylinder diameter 
more nearly represents average practice. This length 
determined, it is only necessary to divide the area of 
the passage by it to determine the width of the port, 
and three fourths of this will give the port opening to 
be used in laying out the diagram. 

A " rule of thumb" which is in very common use is 
to make the steam pipe one fourth the diameter of the 
cylinder, and the exhaust pipe one third. At slow 
speeds this rule gives an excess of capacity over the re- 
quirements, to which of course there is no objection; 
but at high speeds it gives a deficiency. On high grade 
engines, where the best results are sought, steam pipes 
are seen as large as one third and exhaust pipes one 
half the cylinder diameter. 

All the principles thus far given will be found re- 
quired in the solution of the following 

Problem V. — An engine with a 10" X 15" cylinder 
is to run at 200 revolutions per minute. Cut-off is to 
be at f stroke, release at .93 stroke, and lead is to be ^". 
Required the diameters of steam and exhaust pipes, the 




ANGULAR VIBRA TION OF THE CONNECTING ROD. 45 

dimensions of the ports, the travel, and the steam and 
exhaust laps of the valve. 



* THE ANGULAR VIBRATION OF THE CONNECTING ROD. 

As has been explained, the slotted cross-head was 
adopted in the preceding to avoid certain distortions 
which are incident to the use of the connecting rod. It 
is now proper to discuss these distortions, and explain 
the methods for neutralizing their effects. 

With the slotted cross-head the position of the piston 




or cross-head in its stroke for any crank position is found 
by simply projecting the crank position to its horizontal 
diameter, or a line parallel thereto, by means of a straight 
projecting line, as was done in Figs. 12, 22, and 24. Fig. 
25 is a skeleton diagram of the usual connecting rod 
and crank. It is obvious that if the crank pin end of 
the connecting rod be disconnected from the crank pin 
and carried to the centre of the crank shaft the cross- 
head pin will occupy its central position a. If from 
this position the crank pin end be carried to either 
" quarter" position of the crank pin b, c, the cross-head 



46 SLIDE VALVE GEARS. 

pin will be drawn toward the shaft and will occupy the 
position d. For the forward stroke the position of the 
cross-head is measured from e as a starting point, and 
hence the cross-head and piston have moved too far 
by the distance ad. For the return stroke the position 
is measured from f as a starting point, and hence the 
cross-head and piston have not moved far enough by 
the same distance. If the valve motion were laid out 
by the preceding methods to cut off steam at half stroke, 
it would in fact cut off later than half stroke for the 
forward stroke and earlier for the return. The same 
distortion takes place at all other positions of the crank 
except at the centres, though to a less degree ; and it 
follows that all the events of the stroke except the lead 
occur too late in the forward stroke and too early in 
the return. The amount of this distortion can be found 
for any position of the parts, as is done in Fig. 25, for 
the position shown, by striking an arc with radius equal 
to the length of the connecting rod, the distance^ be- 
ing equal to ad. Striking this arc is, in fact, projecting 
the point b to the centre line with the circular arc in- 
stead of a straight line, as has heretofore been done ; 
and in order to find the true relation between the posi- 
tions of the piston and crank, it is only necessary to 
project the one to the other by means of such circular 
arcs with radius equal to the length of the connecting 
rod. It is often convenient to measure the piston posi- 
tions for the forward and return strokes from the same 
starting point as i, and in order to do this it is only 
necessary to strike the arcs for the forward and return 
strokes from opposite sides of the shaft. Thus, with 
the crank on the quarter, the piston will have moved 



ANGULAR VI BRA TION OF THE CONNECTING ROD. 47 

through the distance ih for the forward stroke and ik for 
the return. Similarly, if the crank move through an angle 
ibl for the forward stroke, the piston will have moved 
through the distance to ; and if the crank move through 
the same angle from p on the return stroke the piston 
will have moved through the distance iq. The directions 
of these distortions for the two strokes are best distin- 
guished by remembering that the effect of the connect- 
ing rod is always to draw the piston too near the crank. 

The amount of these distortions will diminish if the 
length of the connecting rod be increased, and if a con- 
necting rod of infinite length be conceived, the distor- 
tions will disappear. Hence a piston motion without 
distortion, such as is given by the slotted cross-head, is 
often called the motion due to a connecting rod of in- 
finite length. 

Since the speed of the crank's rotation is uniform, 
and the piston must travel farther for a given angle of 
crank rotation in the forward than in the return stroke, 
it follows that the speed of the piston's motion is greater 
in the forward than in the return stroke. 

These principles can be applied to the problems al- 
ready given, and thereby determine the actual positions 
at which the various events occur. Fig. 26 is a repro- 
duction of Fig. 22, but with the projections made by 
circular arcs instead of straight lines. It thus appears 
that with the valve there designed, the cut-off, instead 
of taking place as intended in Fig. 22, will really take 
place after a piston travel Aa f , Fig. 26, in the forward 
stroke and Aa" in the return. Similarly, the compres- 
sion will take place after travels Ah' and Ah" > and the 
release after Ab' and Ab" . If preferred, the construe- 



48 



SLIDE VALVE GEARS. 



tion may be made by repeating the lap circles below 
the centre line in position for the return stroke, as is 




a" & nnm 



Fig. 26 



done in Fig. 27. With this construction the measure- 
ments are necessarily made from A for the forward 
stroke and B for the return. Of these two plans that 
of Fig. 26 possesses the advantage that it shows at a 
glance the difference between the points of cut-off, etc., 
in the two strokes. 

Problem VI. It is required to find the true positions 
for cut-off, release, and compression of the valve of 






ANGULAR VIBRATION OF THE ECCENTRIC ROD. 49 




Fig. 27 

Problem III. Length of connecting rod five times the 

crank. 

* THE ANGULAR VIBRATION OF THE ECCENTRIC ROD. 

As has been explained, the eccentric is in effect a 
crank and the distortions introduced by the connecting 
rod into the motion of the piston are likewise intro- 
duced by the eccentric rod into the motion of the valve. 



SO SLIDE VALVE GEARS. 

In other words, if the distortions are not corrected, the 
valve, like the piston, will always be too near the crank. 
The throw of the eccentric is much less than the arm 
of the crank, and the eccentric rod is proportionately 
longer than the connecting rod ; hence the distortions 
in the positions of the valve are absolutely and relatively 
smaller than those in the positions of the piston. Since 
the effect of these distortions is to draw the valve too 
near the crank, it follows that if they are not provided 
for, the lead of the valve at the back end f of the cylinder 
will be increased and for the front end diminished. The 
greatest port openings are measured with the eccentric 
on the centre line of the engine, when these distortions 
vanish ; and hence the two port openings will be equal 
It is important that the lead openings be equal, while 
it is not particularly important that the maximum port 
openings be equal, provided the smaller one be large 
enough. Hence in practice the eccentric rod or valve 
rod is slightly lengthened to give equal lead at the two 
ends, and the result is that the port opening is slightly 
diminished for the forward stroke and slightly increased 
for the return. This lengthening of the eccentric rod 
is effected in setting the valve for equal lead, and it 
practically corrects the effects of the angular vibration 
of the eccentric rod. 

* EQUALIZED EXHAUST. 

As has been explained, the setting of the valve for 
equal lead practically neutralizes the effect of the an- 

f With apologies to the locomotive fraternity, the end of the cylinder 
farthest from the crank will be called the back end. 



EQUALIZED EXHAUST. 



51 



gularity of the eccentric rod. Nothing, however, has 
yet been done toward correcting the irregularities due 
to the connecting rod, and that is the next subject to 
be discussed. 

If the valve has no inside lap, compression and re- 




Fig. 28 



lease are coincident, and the correction of one will like- 
wise correct the other. It is desired to cause both these 
events to occur earlier in the forward stroke and later 
in the return stroke, and to accomplish this, it is only 
necessary to give an appropriate exhaust lap to the end 
of the valve nearest the crank shaft, and an equal nega- 



52 



SLIDE VALVE GEARS. 



tive exhaust lap to the other end. In applying this cor- 
rection, it should be remembered that the Bilgram dia- 
gram gives the true relation between the positions of 
the crank and eccentric, and that the distortions under 
discussion are given to the piston through the connect- 
ing rod. In Fig. 28 it is proposed to correct the release 
and compression of the valve shown, which, in the first 
instance, has no exhaust lap. By the vertical projec- 
tion lines the points of release a, b are found in the usual 
way, and by means of the curved projection lines points 
a\ fi'are found for the correct crank positionscorrespond- 
ing to piston positions^, b. If the release and compres- 
sion are to take place at piston positions a, b, they must 
take place at the crank positions a', b f . Drawing the 
crank lines #'<9and b'O, it is easy to add the exhaust lap 
circles shown, from which measurement shows that for 
that edge which effects exhaust at a! a positive lap of 
yV' is required, and for V a negative lap of the same 
amount. The resulting valve is shown in Fig. 29. Had 




Fig, 29 

the valve originally possessed exhaust lap, as in Fig. 
30, exact equalization would have been impossible, al- 
though a result could have been reached sufficiently near- 
ly correct for all practical purposes. The piston positions 



EQUALIZED EXHAUST. 



53 



for compression a, b and releaser, d are projected to the 
crank circle by circular arcs, as shown, giving the corre- 
sponding crank positions a', b ' , c\ d\ It is apparent at 
once that the change of lap to give compression at a' is 
greater than the change to give release at d\ and simi- 





^-" 


^ 






^ 


V. 




S 


V. 


/ 


/ 
^ 


X.,^^^ 


/ 

/ 


/ 


//vhN \ 


/ / 


f/y{\h^' ] 


/ / 




/ / 




)( / V ^sv\L*^^ 1 


/ / 




s)\ ^^^^\ ^ / 


/ / 




y^V^/O^ j|\ ji y 


/ 1 




^ \/C^ a \ |/\ 


\ i 




^^^^^^^^ 1 ^ ^x^ 


\ 


id b 




&*^ ^ ft 


\ 


\ i h 

1 ^Xi 




a c j 






/ 1 


A L^ 




/ / 


i i iU<fl^ 




/ / 


l d viK 




/ / 
/ / 






/ / 


\ 7VT*? 


\ / 


/ / 


\ 6x x 


\ / 


y / 


>s^J 


^/ "^ 


/ 




\ 


- y 




>* 


**■ 




>■* 


**- 






<0-* 0k 





I 



Fig. 30 

larly for c' and b\ In such a case the best that can be 
done is to divide the difference, making the alteration in* 
the lap half way between that called for by a r and d' for 
their end of the valve, and half way between that called 
for by d and b f for their end of the valve. This sub- 
ject wi!4 be returned to at the close of the next section. 



54 SLIDE VALVE GEARS. 



EQUALIZED CUT-OFF. 



It was shown in the last section that by introducing 
inequality in the inside laps, the inequality of release 
or compression could be equalized — a change in one 
event being, however, accompanied by a change in the 
other. It is obviously possible to equalize the cut-off 
in a similar manner by making the outside laps un- 
equal. As a change in the inside laps involved both 
release and compression, so will a change in the outside 
laps involve both admission and cut-off ; and since the 
valve, as thus far described, gives equal lead at the two 
ends of the cylinder, it follows that increasing one lap 
and decreasing the other would result in an unequal 
lead — in other words, cut-off equalized by such a 
method would involve unequal lead. Such a method 
is usually explained in detail in books of this character. 
Equality of lead is, however, of more importance than 
equality of cut-off, f and hence the method is of no 
practical importance, and is not introduced here. 

The following method secures equality of cut-off 
without affecting the equality of the lead. It has 
no objectionable features, and is of general utility. 
Throughout the discussion, one fundamental fact must 
be kept in mind, viz.: The acts of opening and closing 
a port by a slide valve differ only in the direction of 
motion of the valve. The port is opened or closed, as 
the case may be, by the edge of the valve passing the 

f Except in vertical engines where the lead for the lower centre 
is usually made larger than for the upper to compensate the action 
of the weight of the reciprocating parts. 



EQUALIZED CUT-OFF. 



55 



edge of the port, and the position of the valve when 
cut-off takes place is the same as when admission takes 
place. Since the valve is mechanically connected to 
the eccentric rod pin, it follows that the position of that 
pin must be the same at cut-off as at admission. 

Let it be proposed to design a slide valve to cut off 
steam at half stroke, with equal lead and cut-off. 




First design the valve by the methods already ex- 
plained, then strike the crank and eccentric circles of 
Fig. 31.* Locate points A, B, the positions of the crank 
pin for admission of steam, and the corresponding 
positions a y b for the eccentric centre. With radius 
equal to the length of the connecting rod, and with 

* In this and the following diagrams the throw of the eccentric is 
made disproportionately large, and the eccentric rods disproportion- 
ately short, to add to the clearness of the constructions without un- 
necessarily large diagrams. This gives the appearance of a distorted 
valve movement ; but with working proportions these apparent dis- 
tortions are no greater than with the usual construction, and are not 
objectionable, 



56 SLIDE VALVE GEARS. 

centre at the middle position of the cross-head pin, 
strike arcs cutting the crank circle at c and d. Before 
cut-off in the forward stroke, the crank shaft, and with 
it the eccentric, must turn through the angle Ac, and 
in the return stroke Bd. Space off a ' e equal to Ac, 
and b'f equal to Bd. Draw eg and fg, and we have 
point h, where the eccentric centre must be for cut-off 
at c, and i where it must be for cut-off at d. With 
radius equal to the length of the eccentric rod, and with 
centres at b y i, strike arcs meeting at k y and with same 
radius and centres a, h y strike arcs meeting at /. Now 
for admission at A and cut-off at c 9 the eccentric rod pin 
must be in the same position, and as the eccentric rod 
is of fixed length, this position must be /, that being 
the only point whose distance from both a and h equals 
the length of the eccentric rod. Similarly for admission 
at B and cut-off at d, the pin must be at k. The pin 
can be brought to these positions at the proper time by 
introducing a rock shaft in the valve motion having its 
centre at any point o ; such that an arc struck from it 
shall pass through k and /, and then connecting the 
eccentric rod to it as shown. The valve stem should 
then be connected to the rocker, as shown at m, n. 
The eccentric rod positions for crank positions A, B 
are shown at al, bk. The rocker fulcrum might be 
located above the centre line, if preferred, at o' . 

In cases where the valve chest is located on the top 
of the cylinder, a rocker of different type, with the arms 
on opposite sides of the fulcrum, becomes necessary. 
The construction for this type of rocker is essentially 
the same as shown in Fig. 32, which is lettered to cor- 
respond with Fig. 31. Of course, with this type of 



EQUALIZED CUT-OFF. 



57 



rocker the eccentric positions a, b change places as 
shown. One result of the equalization growing out of 
the inequality of the rocker arms is to alter the port 
opening from that determined upon in the original de- 
signing of the valve. The motion as thus far deter- 
mined should therefore be treated as a trial result only, 
and the dimensions of the valve and eccentric should 
be altered in the light of the experience gained. 



n m 




At the close of the description of Fig. 31 it was 
stated that the rocker fulcrum might be located indif- 
ferently at either or o' of that figure. This is strictly 
true so far as relates to equal lead and cut-off, but there 
is still a difference in the effect of the two positions. 
By suitably locating the fulcrum the compression and 
exhaust can be equalized for the two ends of the cylin- 



58 



SLIDE VALVE GEARS. 



der — exactly if the valve have no inside lap, and ap- 
proximately if it have such lap. This has not the 
unique interest which belongs to the equalization of lead 
and cut-off, since it can be accomplished by other 
means; but it forms an interesting study, nevertheless. 
The method of accomplishing this equalization is 
shown in Fig. 33, which follows the construction of Fig. 



/ / 
/ 1 

/ 1 










r 


' 1 

/ I 






f* 




rx«' 


f 1 

/ / 










i* yy\ 


/ / 








/£l 


L~^a, 1 \ 


^^^r J 






~**nl 




/ J 1 Vb 


iri^ - *^ 


— ^ 


-41 


i — —J- 


%* 


X 7) VM 1 


Fig. 


33 




\l / 







31 up to and including the finding of k, /, but with lead 
zero. Suppose, in the first instance, that the valve has 
no inside lap, and by the methods already described 
find the points of the piston stroke m ) n y where release 
and compression should occur, and by arcs whose com- 
non radius is equal to the length of the connecting rod 
find the corresponding crank positions^,/. Layoff 
Acs from a giving q, and Bdp from V giving r. Draw qg 
and rg giving t and «, where the eccentric must be for 
the two equalized compressions. With radius equal to 
the eccentric rod, and centres t, u, strike arcs meeting in 



SETTING THE SLIDE VALVE, 59 

v. Now locate the rock shaft fulcrum at o, such that 
the eccentric rod pin shall pass through k, /, and v, and 
the result will be a valve motion giving equal lead, cut- 
off, release, and compression. If the valve have inside 
lap, then, instead of one point, v, there will be two, 
just as with outside lap there are two points, k, L In 
that case it will be found impossible to so locate o that 
the eccentric rod pin shall pass exactly through all four 
points. It should be then made to pass through k and 
/, and the difference be divided between the two points 
v. The release and compression will then be as nearly 
equalized as is possible. 

SETTING THE SLIDE VALVE. 

As the parts of an engine valve motion are assem- 
bled two dimensions are lacking: 1st, the angular loca- 
tion of the eccentric relative to the crank ; and, 2d, the 
length of the valve rod. The eccentric is capable of 
being located in any angular position, and the length of 
the valve rod is usually capable of adjustment by means 
of jamb nuts each side of the valve, or some equiva- 
lent means. The setting of the valve involves locating 
the eccentric and fixing the valve at the proper point 
on the rod. There are two distinct steps to the process : 
I. Locating the engine exactly on the centre ; 

II. Locating the eccentric and valve. 

To locate the engine on the centre, proceed as fol- 
lows : Turn the crank to any convenient distance 
above the centre, Fig. 34. Upon the side or face of the 
crank disc or fly-wheel, as most convenient, scribe an 
arc a by means of a tram b swinging from any conven- 



6o 



SLIDE VALVE GEARS. 
I 




SETTIXG THE SLIDE VALVE. 6 1 

ient fixed point on the engine frame or floor. Also 
scribe a line c on cross-head and guides. Turn the crank 
below the centre as shown by Fig. 35, the cross-head 
line receding from its mate on the guide and approach- 
ing it again. When these lines are exactly fair, stop 
the motion and scribe a second line d on the wheel, line 
a, now occupying the position shown in Fig. 35. With 
the dividers find point e, dividing the arc ad in halves. 
When point e is brought fair with the point of the tram, 
Fig. 36, it is clear that the engine will be on the centre. 
Repeat this construction for the other centre. One pre. 
caution is necessary in relation to the above, in order to 
obviate any error that might arise from looseness in the 
crank pin and cross-head pin bearings : In scribing the 
lines a and d have the crank pin pressing against the 
same brass for both lines. It matters not which brass 
be used, but the same one must be used for both lines. 
To locate the eccentric and valve proceed as follows: 
Locate the eccentric by the eye as near as may be, 
and ahead of its correct position rather than behind it. 
Bring the engine to either centre, as found above, turn- 
ing it in doing so in the direction of the proposed rotation 
in order to neutralize any looseness in the connections. 
With the engine on the centre, locate the valve to give 
the required lead, after which turn the engine in the 
direction of its future rotation to the opposite centre. If 
the eccentric is ahead of its correct position, the lead 
for this position will be greater than the first ; if the 
eccentric is behind, the second lead will be less than 
the first, and probably negative. In either case the 
valve is to be adjusted on the rod to divide the differ- 
ences in the lead. This being done, the valve is cor- 



62 



SLIDE VALVE GEARS, 




5S 



3 



SETTING THE SLIDE VALVE. 63 

rectly located on the rod, the lead is equal at the two 
ends of the cylinder, but is too large or too small at 
both. To correct this it only remains to adjust the 
eccentric, moving it in the direction of the rotation until 
the valve have the proper lead. Verify the results, 
and the work is done. 



Part II. 



THE SLIDE VALVE WITH SHIFTING 

I 

AND SWINGING ECCENTRIC. 



The Slide Valve with Shifting and 
Swinging Eccentric. 



THE SLIDE VALVE AT SHORT CUT-OFF. 

The difficulties which impede the use of the plain 
slide valve at short cut-off have been explained at 
length in Part I. Before explaining the shifting eccen*. 
trie automatic valve gear, it is necessary to show how 
these difficulties have been surmounted. By referring 
to the section on the Limitations of the Plain Slide 
Valve those difficulties will be seen to be — 

I. Premature release and compression — either of 
which, however, can be made later at the expense of 
making the other earlier still. 

II. Inadequate port opening to steam or, in lieu of 
that, excessive size and travel of valve. 

The first difficulty has been met by increasing the 
speed of the engine. All of the engines employing 
this description of valve gear are of the " high speed" 
type. In such engines a heavy cushion is appropriate 
and necessary to bring the reciprocating parts quietly 
to rest at the centres, and hence the early compression 
ceases to be a radical objection. Indeed, inside lap is 

67 



68 SLIDE VALVE GEARS. 

given to the valve in order to delay the release — there- 
by, as has been explained, still further increasing the 
compression. 

The second difficulty is met by two expedients, the 
first being sometimes employed alone, but more often 
in connection with the second. These expedients are, 
1st, the use of balanced \ r alves, usually of the true pis- 
ton type or of the " pressure plate" type, both being 
perfectly balanced against the steam pressure ; 2d, the 
use of valves having multiple ports, by which the neces- 
sary throw of eccentric is halved or even quartered. 
The use of balanced valves permits the use of valves of 
large size and great throw; and the use of multiple 
ports gives sufficiently large openings with such throws 
as it is practicable to use. 

It is believed that the first engine to embody the 
above features in connection with a shifting eccentric 
and a shaft governor w T as the Straight Line ; and hence 
that engine is entitled to be recognized as the progeni- 
tor of a large and vigorous family. So far as known, 
these features were first combined in an engine designed 
by Professor John E. Sweet, built at the Cornell Uni- 
versity shops, and exhibited at the Centennial Exhibi- 
tion. 

That the difficulty of restricted port opening is a real 
one, maybe gathered from any indicator diagram from 
a locomotive with plain valve at good speed and well 
" notched up." Such diagrams invariably show a 
marked fall in the steam pressure on entering the cyl- 
inder ; and it is largely on this account that such per- 
sistent attempts have been made to improve the loco- 
motive valve motion. An appropriate introduction to 



THE SLIDE VALVE AT SHORT CUTOFF. 



6 9 



the study of multiple ported valves is found in one not 
necessarily balanced, which was designed more especial- 
ly for use on locomotives, — to which, it has been large- 
ly applied, — namely, the Allen valve, shown in Fig. 37. 
In this valve the seat is shortened and a supplement- 
ary port aa is cast through the valve. This port regis- 
ters with the end of the seat as shown in the figure, 
which represents the valve open by the amount of its 
lead. The course of the steam is shown by the arrows, 
from which it will be seen that the opening at b is added 




Fig. 37 

The Allen Valve. 

to the usual one at c ; and that up to the point where 
the opening at c is equal to the width of passage a, 
the total opening is just twice what it would be with 
the usual form of valve. 

The " pressure plate" type of valve is well shown in 
Fig. 38, which represents the valve of the Straight Line 
engine. The pressure plate AA receives the pressure 
of steam upon its back. It is prevented from pressing 
the valve proper to its seat by means of distance pieces 
above and below the valve, and slightly thicker than the 
valve. Recesses in the plate form in it an exact coun- 



7o 



SLIDE VALVE GEARS. 



terpart to the valve seat. The valve slides between 
the seat and plate like a square piston relieved of all 
pressure. This valve, like those that follow, is shown 




Fig. 38 

The Straight Line Valve. 

open to its lead ; and the manner in which the recesses 
in the plate and the passages aa through the valve 
combine to give a double port opening will be seen 




Fig. 39 

The Woodbury Valve. 

from the arrows. The ledges bb are for the purpose of 
protecting the finished surfaces of the pressure plate 
from the cutting action of the exhaust steam. Some 
designers of double ported valves have thought it best 
to provide double ports for the exhaust, while others 



THE SLIDE VALVE AT SHORT CUTOFF. 



71 



have not. The illustrations of both the Allen and 
Straight Line valves will show that the opening to ex- 
haust is amply large without double ports ; but such 
ports increase the quickness of opening to exhaust, and 
so secure a desirable advantage. The valve under dis- 
cussion is provided with them at c, c. Their action is 



V- 



N \ 



I 






Fig. 40 



precisely the same as that of the steam passages a, a, and 
need not be explained further. 

Fig. 39 shows the valve of the Woodbury Engine Com- 
pany. It combines the method of action of the Allen and 
Straight Line valves, and so secures four port openings 
to steam and two to exhaust. Openings a, b act pre- 
cisely like those of the Straight Line valve, and open- 
ings c, a act substantially like the supplementary port of 
the Allen valve. This will be seen more clearly by re. 



72 



SLIDE VALVE GEARS. 



ferring to Fig. 40, which represents a plan of the Wood- 
bury valve. Passages ^,/*are cast through the valve to 
act in conjunction with the openings c, d of Fig. 39, in 
the same manner that the passage aa of Fig. 37 oper- 
ates in conjunction with opening b of the same figure. 
Ledge g acts to protect the finished surfaces of the 
cover plate from the action of the exhaust in the same 
manner as ledges b, b of the Straight Line valve. 

Fig. 41 illustrates the valve of the Armstrong engine, 




Fig. 41 

The Armstrong Valve. 

in which the action of the steam and exhaust edges of 
the valve is reversed from the usual practice. The 
steam enters at #, and the outer edges of the valve con- 
trol the exhaust. The steam pressure tends to lift the 
cover plate, and it is therefore held down to its seat by 
means of the bridle b. The action of the steam ports 
will be seen from the arrows. This valve gives four 
openings to steam and two to exhaust. 

The Rice valve (Fig. 42), like the last example, takes 



THE SLIDE VALVE AT SHORT CUTOFF. 



n 



steam from the inside. It gives two openings to steam 
and two to exhaust. The relief plate aa is in this in- 
stance a piston fitting the cylinder 6&, this cylinder be- 




Fig. 42 

The Rice Valve. 

ing bolted to the floor of the steam chest. The pres- 
sure of steam within this cylinder forces the piston 
/ toward the valve, which, however, it is prevented from 




Fig. 43 

The Armingion and Sims Valve. 

touching by means of distance pieces slightly thicker 
than the valve, and similar to those already described 
in connection with the Straight Line valve- 



74 



SLIDE VALVE GEARS. 



Fig. 43 illustrates the Armington and Sims valve, 
which is a true piston valve with double ports. The 
course of the steam is shown as heretofore by the 
arrows. 

Fig. 44 shows the Ide double ported valve, which, 
like the last, is a piston valve. 




Fig. 44 

The Ide Valve. 

Of an entirely different type is the Giddings valve as 
used in the Russell & Company engine. This valve is 
shown in Fig. 45. Steam enters at a and exhausts at bb. 
Each end of the valve acts in much the same manner 
as the Allen valve, as will be understood from the arrows, 
while over all is cast a case c. The steam entering from 
the inside of the valve, its pressure would, if not coun- 
teracted, lift the valve from its seat. This is prevented 
Sy the use of "needle ports" (not shown), one connecting 
che live steam space within the valve to the body of 
the valve chest, and the second connecting the chest to 
the exhaust. The action of these ports is explained by 
Mr. Giddings as follows : " The steam is taken under 
the valve, which would result in throwing the valve off 






THE SLIDE VALVE AT SHORT CUTOFF. 



75 



the seat. This must be counteracted by pressure on 
the back of the valve sufficient to overcome the ten- 
dency to leave the seat. This I obtain by the small 
needle port communicating with the live steam passage 
on the inside of the valve. If there were no outlet 
this would soon result in an excess of pressure nearly 
equivalent to steam pipe pressure on the back of the 
valve, which would produce a hard working valve. To 
avoid this, I put another needle port opening, commu- 
nicating with one of the exhaust * D's ' of the valve. 

C 



ssss^^\S^>*S^^ 




Fig. 45 

The Giddings Valve. 

The resulting pressure due to these two openings is 
just sufficient to overcome the tendency to leave the 
seat." 

A remarkable feature of this valve, not attained by 
any other so far as known to the author, is the use 
made of the supplementary passage d. After the com- 
pression has commenced, and before opening to admit 
live steam from the steam supply, this passage opens 
into communication with the regular steam port. This 
increases the volume into which the steam is compressed, 
without, however, increasing the clearance space from 
which the steam is exhausted, since this supplementary 



76 SLIDE VALVE GEARS. 

port is never in communication with the exhaust. This 
is described by Mr. Giddings as follows : 

" We find by increasing the capacity of the carry over 
port or portchamber, that we can use it as a reservoir 
or port into which to pack the surplus compression of 
a single valve automatic movement, thereby giving us 
a peculiar offset in the compression curve, and giving 
us from 10 to 12 per cent increase of area, and a con- 
sequent increase of power from a given sized engine. 
The amount of this is entirely within our control by a 




Fig. 46 

variation of the cubical capacity of this passage way, 
thereby enabling us to get the compression curve down 
in the corner, something after the manner of the four 
valve engine cards. " 

This feature is of such unique interest that indicator- 
cards from one of these engines (Fig. 46) are introduced 
to illustrate it. The offset mentioned will be seen at 
aa, the dotted line b representing the compression 
curve that would have resulted but for this provision. 

The shifting eccentric valve gear, in connection with 
which all these valves are used, requires that the valve 



EQUAL LEAD AND CONSTANT LEAD. 77 

shall have an excess of port opening and travel at the 
late cut-offs in order that they may be sufficient at the 
early cut-offs. Inspection of any of the valves illustrated 
will show that with large travels the supplementary port 
becomes closed after the main port is well opened ; and 
with such travels the effect of the supplementary port is 
merely to increase the quickness of port opening and 
closing. 



* EQUAL LEAD AND CONSTANT LEAD. 

The lead of a valve may vary in two ways, and to 
prevent ambiguity it is necessary to define and follow 
an exact use of terms. The reader is asked to note 
carefully the following explanations of the terms equal 
lead and constant lead. They will be used hereafter 
strictly as defined, and it is necessary that they be 
clearly understood. 

Equal lead implies that the lead is alike at the two 
ends of the cylinder. Constant lead implies that the 
lead does not change for different grades of expansion. 
An engine might have equal lead for one grade of ex- 
pansion and unequal lead for another grade, or the 
lead might be equal at all grades without being con- 
stant ; that is, the lead at the two ends of the cylin- 
der might be always alike, but larger at both ends for 
three quarters cut-off than for one quarter. So, also, 
an engine might have constant lead without equal lead ; 
that is, the lead might not change for different grades 
of expansion, but at the same time be always larger 
for one end of the cylinder than for the other. 

The above distinctions are radical and important, 



78 SLIDE VALVE GEARS. 

and it is necessary that they be clearly seen in order to 
understand what follows. 



THE SHIFTING ECCENTRIC, f 

The expedients which are employed for making what 
is geometrically the plain slide valve available for early 
cut-offs having been explained, it remains to describe 
how the same valve can be made available for different 
cut-offs. 

In Fig. 47 let the circle abc represent the eccentric 
path of a given eccentric in the Bilgram diagram, the 
eccentric centre being at d, and L and / being, as usual, 
the steam and exhaust lap circles. Let the centre of 
the eccentric be shifted from d to d ; , dd r being a 
straight line perpendicular to ac. There will thus be 
formed a new eccentric path a'b'c'. Laying off b r d r up- 
ward from c' , will locate Q', the new centre of the lap 
circles. From this centre the lap circles maybe drawn 
in the usual way, and from them the crank positions A 
for the new point of cut-off, B for exhaust closure, and 
C for release may be found. Since &/ equals cQ, and 
b'd' equals c'Q', and since dd f is perpendicular to ac, it 
follows that QQ ' is parallel to ac : hence the lead open- 
ing has not been changed. The lead angle, however, 
has clearly been increased, and the port opening has 
been reduced. In the same way, the eccentric may' be 
shifted still further on the line dd' , and new points of 
cut-off, release, and compression, and new values of the 

f Throughout this and the following section the angularity of the 
connecting and eccentric rods is neglected. 



THE SHIFTING ECCENTRIC. 



79 



port opening, found. Finally, if the eccentric be shifted 
to the position d° on the line ac, the point Q will be lo- 
cated at Q°, when the port opening will be reduced to 
the lead opening and the cut-off will take place as much 
after the centre as the lead did before it. In all posi- 

A 




Fig. 47 



tions the lead opening will be constant. If the valve 
have multiple ports, when the travel becomes so reduced 
as to bring them into action, the result will be to give 
double or quadruple the opening shown by the diagram, 
as the case may be. Should the movement of the ec- 
centric be continued below the line ac, the result wouid 



80 SLIDE VALVE GEARS. 

be to reverse the direction of the rotation. The study 
of reversing engines is, however, beyond the scope cf 
the present work. 

An eccentric arranged for adjustment on straight 
line dd°, as in this illustration, is called by the author a 
shifting eccentric* 

So far as known to the writer, there are but two en- 
gines in the American market which employ a shifting- 
eccentric. These are the Armington and Sims and the 
Russell (Giddings) engines. The former obtains prac- 
tically a straight line motion of the eccentric centre by 
means of a combination of two eccentrics, while in the 
Russell engine the required motion is obtained by means 
of a straight guide keyed to the shaft and appropriate 
wings attached to the eccentric. 

THE SWINGING ECCENTRIC. 

Instead of shifting the eccentric across the shaft in a 
straight line as in the last examples, most designers have 
preferred to swing it by an arm cast in one with itself, 
and pivoted to an arm in the fly-wheel or other con- 
venient piece. Such an eccentric is called by the author 
a swinging eccentric, and its effect upon the steam dis- 
tribution, as distinguished from the shifting eccentric, 
is to vary the lead opening at different points of cut-off. 
The nature and degree of this variability depends in 
large degree upon the location of the pin from which 

* For want of another word, the term shifting eccentric is also used 
as a general expression which includes both shifting and swinging 
eccentrics. This double use of the word will not, however, cause con- 
fusion. 



THE SWINGING ECCENTRIC. 



81 



the eccentric is swung. If the pin is on the same side 
of the shaft as the crank, and in the centre line of the 
crank, as in Fig. 48, the path of the eccentric across the 
shaft is the arc dd°. The path of the point Q will then 
be a similar arc QQ°, with the same radius and with its 
centre located in the line ef. It is clear from the posi- 
tions of the various lap circles that the lead opening 




/ 
Fig. 48 

will not be constant with this arrangement, but will be 
greater in the early cut-offs than in the late ones. The 
action upon the other events of the stroke is substan- 
tially the same as that of the shifting eccentric. With 
the pin located in the centre line on the opposite side 
of the shaft from the crank, as in Fig. 49, the arc in 
which the eccentric swings has its convexity reversed 



82 



SLIDE VALVE GEARS. 



from the last figure. The path of the point Q will also 
be reversed, and instead of receding from the centre- 
line in the early cut-offs, it will approach it, thus dimin- 
ishing the lead opening in those cut-offs. This diminu- 
tion of lead may be carried so far as to make the lead 
zero or even negative in the early cut-offs — a fact which 




fig. 49 



will be shown on the diagram by the earlier steam lap 
circles crossing the horizontal centre line. The same 
result of a decreasing lead in the early cut-offs can be 
obtained with the eccentric swing pin on the same side 
of the shaft as the crank, but raised above the centre 
line as in Fig. 50, in which the swing pin is located on 
the line dg extended. Similarly, by raising this pin 
when located opposite to the crank, an increasing lead 
can be obtained. By locating the pin half way between 



THE SWINGING ECCENTRIC. 



83 




* 


Fig. 


50 




i 1 K - 




-f— 


\y x \ y / 

fh 1 I 






^ 




Fig 


5/ 



8 4 



SLIDE VALVE GEARS. 



the positions of Figs. 48 and 50, on the line hi of Fig. 
51 the lead will be the same at the smallest as at the 
greatest throw ; and by suitably placing it as in Fig. 52, 
the lead can be made alike for any two expansions de- 
sired. In this construction the two points of cut-off 




Fig. 52 



for which equal lead is desired are decided upon, and 
the corresponding crank positions A, B are drawn. The 
lap circles are drawn in the usual way for A and B, 
the lead being made the same for both. Points Q and 
Q r are then transferred to d and d\ and the eccentric is 
so hung that its centre shall pass through the points 
d and d' . 



THE ANGULARITY OF THE ECCENTRIC ROD. 85 

As has been pointed out, if the valve have a negative 
lead in the early cut-offs, it will be shown in the diagram 
by the lap circle going below the horizontal centre- 
line. In this case if the cut-off be made early enough 
the lap circle will pass through the centre of the shaft. 
This marks the point where the port opening becomes 
zero by reason of the eccentric throw becoming re- 
duced to equality with the lap. For any smaller throw 
there is no admission whatever. 

Designers have usually endeavored to obtain as nearly 
a constant lead as possible. The author considers, how- 
ever, that for stationary engines, where the speed is 
fixed, a lead decreasing in the early cut-offs is more 
suitable. That the lead should be equal at the two 
ends of the cylinder, there is, however, no question. 
This entire subject will be discussed at greater length 
in the section on Equalized Lead. 

*THE ANGULARITY OF THE ECCENTRIC ROD. 

Thus far in Part II the influence of the angular vi- 
bration of both connecting and eccentric rods lias been 
ignored. It will be understood that primarily both 
connecting and eccentric rods produce the same distor- 
tions with the shifting as with the fixed eccentric. 
There is, however, with the shifting or swinging eccen- 
tric an additional distortion produced by the angularity 
of the eccentric rod growing out of the fact that the 
vibration of that rod varies in amount with the varying 
throw of the eccentric — the small throw due to an early 
cut-off giving a small angular vibration, and the large 
throw due to a late cut-off giving a larger vibration. 



86 



SLIDE VALVE GEARS. 



Taking up first the case of the shifting eccentric in 
Fig. 53,* let A, B represent the crank pin of a shifting 
eccentric engine when on the dead centres, a, b being 
the corresponding positions of the eccentric centre at its 
greatest throw, h> i at its mean throw, and ^,/at its 
smallest throw. The positions of the eccentric rod for 
mean throw of the eccentric are shown at ch, di, and 
the valve in both positions is open by the amount of 
its lead, as shown by the upper valve sketch for c\ and 
the lower one for d. Let the path of the eccentric 




centre, when shifted across the shaft to change the ex- 
pansion, be a straight line occupying the position ae 
for crank position A, and bf for crank position B. Im- 
agine the crank on the centre A, and shift the eccen- 
tric toward e. Obviously point c will be moved to the 
left, and the lead will be disturbed. For crank posi- 
tion B the same is true ; and what is still worse, while 
the movement for crank position A decreases the lead, 
that for B increases it. If, with crank at A, the eccen- 
tric be shifted towards a, and with crank at B towards 

* See foot-note, page 55. 

This feature of the present diagrams shows a greater irregularity in 
the lead in the usual form of construction, as well as in the form to be 
described, than actually obtains with working proportions. This, how- 
ever, for the present purpose, is rather an advantage than otherwise. 



THE ANGULARITY OF THE ECCENTRIC ROD. 87 

b, the lead at the two points will be disturbed in the op- 
posite directions; i.e., for position^! the lead will be in- 
creased, and for B decreased. The broad fact is evi- 
dent, that, owing to the varying angularity of the ec- 
centric rod, an engine laid out as shown in Fig. 53 could 
not have a constant lead, and it could only have an 
equal lead for some one (selected) grade of expansion. 
With a swinging eccentric, the simplest case is where 
the eccentric swings about a point which, with crank 
at A, Fig. 54, coincides with c. Thus, suppose a 




Fig. 54 b 



large disc keyed to the shaft, and arrange the ec- 
centric to swing about a pin fixed to the disc, the 
centre of the pin for crank position A coinciding 
with c, Fig. 54. Now shift the eccentric from h to- 
wards e or 0, and c will not be disturbed. When, 
however, the crank is at B, the pin c will be at g\ and 
if the eccentric be shifted from i towards/" or &, point d 
will obviously be disturbed more than in the corre- 
sponding movement of Fig. 53; and it may be said in 
general, that with the eccentric rod arranged in the 
common way, as shown in Fig. 53, any change in the 
path of the eccentric across the shaft, to correct the in- 
constant lead at one dead centre, will only make mat- 
ters worse at the other, and by no possible modifica- 



88 



SLIDE VALVE GEARS. 



tion can the lead be made equal for more than one 
grade of expansion. 

The arrangement of Fig. 54, however, while of inter- 
est and value in a theoretical study of the subject, is of 
no practical importance, because its use would require 
so large a disc for the attachment of the eccentric 
swing pin as to be impracticable. It therefore be- 
comes necessary to examine the situation with the ec- 
centric swung from a position nearer the shaft. Let 
the pin be located at the centre of the crank pin — a 
common position — as in Fig. 55, the eccentric rod 
being much longer than the crank, as it always is in 
practice. In that case the actual path of the eccentric 




Fig. 55 

for crank at A will be to the right of ae of Fig. 54, and 
to the left of bf\ consequently the lead will increase 
at both ends of the cylinder for short cut-offs, but the 
increase will plainly be greater for crank position B 
than for A. The result is a lead increasing in the early 
cut-offs, but increasing much faster for one end of the 
cylinder than for the other, and hence equal at the two 
ends of the cylinder for one grade of expansion only. 
Similarly it might be shown that by swinging the ec- 
centric from a point diametrically opposite the crank 
pin the lead would decrease in the early cut-offs (see 
Fig. 49), but decrease much more rapidly for one end 



EQUALIZED LEAD. 89 

of the cylinder than for the other ; and it is clear that 
whatever quality is sought for in the lead, and deter- 
mined so far as the Bilgram diagram can do it, it will 
in fact be modified by the angular vibration of the ec- 
centric rod. It seems unnecessary, however, to exam- 
ine the subject in detail further. 

* EQUALIZED LEAD. 

So far as known to the author, the only engine in 
which any attempt is made to correct the distortions 
which have just been explained is the Straight Line. 
The valve motion of this engine, like its mechanical 
details, is an exhibition of refined ingenuity which it 
would be difficult to surpass. In the following it will 
first be explained how the engine was originally built 
to secure a substantially constant lead, and after that 
the present construction will be shown. The con- 
struction to be described is essentially the same as that 
already used in equalizing the cut-off of fixed-eccentric 
engines (page 54), and it should be understood that 
the present use of that construction was the original 
one — its use for equalizing the cut-off being in fact 
an offshoot of its original use for equalizing the lead. 
In equalizing the lead as well as the cut-off, two 
types of rocker are possible. The first type of rocker 
is shown in Fig. 56, the parts being lettered as in 
the three preceding figures. From h and i, he and id 
are drawn parallel to the centre line, and each is 
made equal to the length of the eccentric rod. The 
rocker fulcrum is then so located at that the pin 
for the eccentric-rod shall describe an arc passing 



9Q 



SLIDE VALVE GEARS. 



through c and d. The pin for the valve rod is located 
as usual, m belonging with c, and n with d. The eccen- 
tric is shifted by being swung from a pin, whose loca- 
tion for crank position A coincides with c. As ex- 
plained in connection with Fig. 54, the disturbance of 
the lead for crank position A is thus eliminated. When 
the crank is at B, c is at g in line with id. In this 
position of the parts, shifting the eccentric on the line 




dfwill disturb the lead a trifle, though much less than 
in the constructions of Fig. 53 or 54. We have here, 
then, a construction which eliminates the disturbance 
for crank position A y and practically eliminates it for B, 
and thus secures substantially a constant lead. Com- 
paring Figs. 54 and 56, the essential difference in the 
two plans is apparent. In Fig. 56, ch and di are par- 
allel, and hence both c and g are in line with the eccen- 
tric rod position to which each belongs ; whereas in Fig. 
54 ch and di are not parallel, and hence, while c is in line, 
.f is not, and cannot be made so. The construction so 
far explained, would, however, lead to inconvenient 
dimensions of some of the parts. The centre of motion 
for shifting the eccentric is therefore in practice moved 



EQUALIZED LEAD. 



9* 



inward from c to some convenient point k on the line 
c/i, the eccentric rod pin still remaining at c. The po- 
sition of k for crank at B is of course /. This change 
introduces a trifling error for crank position A, and by 
an equal amount increases the existing error for B\ but 
the final irregularity is infinitesimal as compared with 
Fig. 53 or 54, and the mechanism accomplishes its ob- 




Fig. 57 



ject — obtaining a practically constant and equal lead 
at all grades of expansion. 

The second type of rocker introduces no material 
change in the lay-out. For an engine with the steam 
chest on top of the cylinder it is illustrated in Fig. 57, 
the parts being lettered to correspond with Fig. 56. 
This type of rocker reverses the motion of the eccen* 
trie, and hence positions a, b, change places as shown. 



9 2 



SLIDE VALVE GEARS. 



As the Straight Line engine is actually built, how- 
ever, the steam chest is on the side of the cylinder, and 
hen^e the second type of rocker takes the unusual 
form of Fig. 58. There is, however, no change in the 
essential principle of the construction, which is, that the 
two positions of the eccentric rods which belong with 
crank positions A, B shall be parallel to one another. 
The object of using this form of rocker is as follows: 




This valve motion, like the usual form, when set for 
equal lead, gives a larger port opening for one end of 
the cylinder than for the other. It is well known that 
the speed of the piston is faster in the end of the cylin- 
der farthest from the crank shaft. Now the second 
type of rocker gives the large port opening to that end 
of the cylinder in which the piston travels the faster, 



EQUALIZED LEAD. 93 

while the first form gives the reverse relation. Hence 
the choice in the construction. 

As now built, however, the Straight Line engine has a 
decreasing lead in the early cut-offs, becoming in fact 
negative in the earliest grades. The reason for this 
change in practice is as follows : In shifting eccentric 
engines, as is well known, the compression increases as 
the cut-off grows shorter. The total cushion by which 
the momentum of the reciprocating parts is arrested 
is the sum of the exhaust cushion and the lead cushion. 
Now if the total cushion is to be constant at all points 
of cut-off, as it should be, the lead must decrease as the 
compression increases, and at the early cut-offs the lead 
should be negative. Furthermore, in such engines, as 
has been explained, both the release and compression 
for early cut-offs occur earlier than is desirable. Now 
by laying out two valves for the same cut-off, one with 
positive and the other with negative lead, it will be 
found that the valve with negative lead gives consid- 
erably later release and compression than does the one 
with positive lead. In other words, the introduction 
of negative lead at the early cut-offs, in addition to off- 
setting in a measure the increasing compression, pro- 
longs the expansion, thereby getting more work out 
of the steam, and also delays the compression, thereby 
still further reducing the cushion. The result is accom- 
plished as shown in Fig. 59, which is a modification of 
Fig. 58. The point k, instead of being on the line di, 
is placed above it. This brings / equally below ch> ex- 
tended ; and, as will be seen by referring to the upper 
valve sketch for m and the lower one for n, reduces 
the lead for both crank positions A and B, as the eccen- 



94 



SLIDE VALVE GEARS, 



trie is shifted inward towards e and f. If the elevation 
of k above di is sufficient, the lead at the early cut-offs 
will obviously be negative. To fully appreciate the 
merit of this construction, Fig. 59 should be compared 
with Fig. 53, when it will be seen that while in Fig. 53 
shifting the eccentric inward from h, i 9 decreases the 
lead in the upper valve sketch, it increases it in the 
lower one ; in Fig. 59, on the other hand, shifting the 




el 



eccentric inward from h y z, decreases the lead in both 
valve sketches. 

Again, Fig. 59 should be compared with Fig. 55, and 
with the suggested companion to it having a decreasing 
lead in the early cut-offs, when it will be seen that 
while the plans are essentially alike in having an incon- 
stant lead, they are unlike in that in Fig. 59 the lead 
is substantially equal at both ends of the cylinder 



EQUALIZED LEAD AXD CUT-OFF. 95 

throughout the range, but in Fig. 55 it is equal at one 
grade of expansion only. 

* EQUALIZED LEAD AND CUT-OFF. f 

It has been shown how, by different methods of pro- 
portioning the parts, the same mechanism can be laid 
out at will to give either exact equalization of the cut- 
off in fixed eccentric engines, or approximate equaliza- 
tion of the lead in shifting eccentric engines. It re- 
mains to be shown how a proportion of parts can be 
found which will satisfy both constructions, and thus 
obtain a practically constant and equal lead, an ex- 
actly equal cut-off for any chosen grade of expansion, 
and approximately equal cut-offs for all grades. 

Referring again to Fig. 56, it appears that the funda- 
mental principle of its construction is the diminution 
of the inclination to one another of the lead positions of 
the eccentric rod; and, referring to Fig. 31, it appears 
that the fundamental principle of its construction is 
the direct reverse of this, i.e., the increase of this incli- 
nation. It hence appears at once that the construc- 
tions of Figs. 56 and 31 are incompatible, and cannot 
be reconciled with one another. Comparing Figs. 57 
and 32, on the contrary, it appears that in this general 
way they agree ; but while in Fig. 57 the inclination of 
he and id is reduced to actual zero, i.e., the rods are 
made parallel, in Fig. 32 al and bk are still inclined at 
an appreciable angle. Now the inclination of #/and 
bk to one another in Fig. 32 can be varied at will by 

f First published by the author in the American Machinist for 
March 14, 1889. 



g6 SLIDE VALVE GEARS. 

changing the length of the eccentric rod ; and by 
choosing a proper length they can be made parallel, 
and the proportions so found will satisfy the construc- 
tion for equal lead, and for the particular grade of ex- 
pansion for which it should be drawn for equal cut-off 
likewise. For other grades it will, of course, satisfy the 
construction for equal cut-off only approximately. One 
qualification must, however, be made. In Fig. 57, A 
and B are located at the dead points, while in Fig. 32 
they are located at the points where admission occurs, 
and these are not usually the dead points. It will 
simplify matters to make these points coincide by con- 
sidering, in the first instance, an engine with a lead of 
zero. In Fig. 60 the construction of Fig. 32 is repeated 
for the mean throw of the eccentric and with lead zero, 
but with several lengths of eccentric-rod, giving a cor- 
responding number of points k\ k" , k' n , /', /", I'". It is 
plain that the inclination to one another of k'b and 
Va is less than that of k f, b and l n a, which in turn is 
less than k'"b and I'" a, the degree of inclination de- 
pending on the length of rod used. If a length of rod 
can be found such that its two positions shall be paral- 
lel to one another, the rod so found will obviously sat- 
isfy the constructions for both equal lead and equal 
cut-off. This length is found in the following manner: 
It is obvious that all the points k\ k u , etc., are on the 
straight line pg, and similarly V , l h ', etc., are on qg\ 
therefore, draw pg and qg. Assume a trial length of 
eccentric-rod, and with centres a, b, strike arcs giving 
k, /, such that bk and al are parallel, repeating the 
construction with different lengths of rod until the 
correct length is found. Locate the rocker fulcrum so 



EQUALIZED LEAD AND CUT-OFF. 



97 



that the eccentric rod pin shall pass through k and /. 
Now positions a/, bk obviously satisfy the construc- 
tion for equal cut-off, and, being parallel, they also sat- 
isfy that for equal lead ; and an engine with its valve- 
motion laid out in this manner will have approximately 
equal and constant lead, equal cut-off for that eccen- 
tric throw for which the construction is made, and an 




I^ZSEB 




Fig. 60 



approximately equal cut-off for other positions of the 
eccentric. 

The construction of Figs. 56, 57, and 58 was made 
with the crank on the centre, while that for Figs. 31 
and 32 was made with the crank in position for ad- 
mission of steam, and in Fig. 60 these methods were 
reconciled by supposing the admission to occur on the 
centre. No material error would be introduced if this 



9 8 



SLIDE VALVE GEARS. 



method were followed in all cases ; but if it is desired 
to follow the strictly correct method, it can be done in 
the following manner: Fig. 61 is a reproduction of Fig. 
32, constructed for the mean throw of the eccentric, 
with some additions. Find points b l , a x and k^ , / x cor* 
o 




responding with crank positions A', B\ and draw kjb, 
and l 1 a 1 . Now the construction of Fig. 32 gives the 
positions of kb and la, while it is desired to make k 1 b 1 
and l x a x parallel by suitably selecting the eccentric rod 
length. This should be done by trial, as before, re- 
peating the trial until the desired result is reached. 



Part III. 



THE SLIDE VALVE WITH INDEPENDENT 
CUT-OFF. 



The Slide Valve with Independent 
Cut-off. 



INTRODUCTORY REMARKS. 

An early cut-off being a necessity for an economical 
use of steam, it comes about that with valves of the 
construction previously described the leading consider- 
ations in their design are those pertaining to the steam 
side of the valve. The valve and eccentric being de- 
signed with reference to the steam side, so as to secure 
an early cut-off, there is little that can be done with 
the exhaust side beyond reconciling conflicting require- 
ments as well as possible. In engines provided with 
independent cut-off valves this condition no longer 
holds : the exhaust can usually be arranged to suit the 
designer's fancy; and it hence follows that in such 
engines the leading considerations in the design of the 
main valve are usually those pertaining to the exhaust. 
It is essential that the exhaust have a certain lead, in 
order that the cylinder may free itself of steam, and, 
on the other hand, this lead should be no greater than 
is necessary for this purpose, since that would involve 
exhausting the steam at a point where it might still do 

IOI 



102 SLIDE VALVE GEARS. 

some useful work. The determination of the point of 
release is, therefore, a leading factor in the design of this 
class of valves. It is not to be expected that there will 
be any close agreement in a detail of this character in 
the work of different designers; but, as a general rule, 
modified somewhat by questions of piston-speed, etc., 
it may be said that release should occur at from 93 to 
95 per cent of the piston stroke.* The other event of 
the exhaust side of the valve, the compression, is de- 
termined, it must be owned, largely by the taste and 
fancy of the designer. A late compression by requiring 
a small exhaust lap conduces to a small travel of the 
valve, which, if it is to be unbalanced, is a desirable 
feature. The features of the exhaust side of the main 
valve and the port opening to steam having been 
settled, the steam side is determined by the force of 
circumstances. To give the proper points of exhaust 
opening and closure, the steam lap will usually be 
small and the cut-off late. This, however, is of no 
consequence, as the cut-off valve is introduced for the 
express purpose of providing for it. 

THE GONZENBACH VALVE GEAR. 

A description and analysis of this valve gear is here 
given as an introduction to those which follow. It is 
now seldom employed. It comprises two valve chests, 
two valve seats, and two valves, as shown in Fig. 62. 
The lower or " main valve" is driven by a fixed eccen- 

* In engines of slow rotative speed — for example, Corliss engines 
and others of similar general character — the release will frequently be 
found to be somewhat later than the figure given in the text. 



THE GONZENBACH VALVE GEAR. 



I03 



trie, and determines the admission, release, and com- 
pression of steam. The upper or " cut-off valve" is 
used solely for the purpose of the cut-off, and is usu- 
ally of the gridiron type, in order to secure quickness 
of cut-off with moderate travel. It is driven by an 
eccentric of its own, which, if the expansion is to be 
varied, must be turned forward or backward, as the case 




Fig. 62 

The Gonzenbach Valve, 

may be, on the main shaft. This movement affects the 
angular advance only, and, unlike the eccentric move- 
ments of Part II, does not change the travel of the 
valve.* 

The action of this cut-off valve is different from any. 
thing that has thus far been examined. The previous 

* The following applications of the Bilgram diagram to the Gonzen- 
bach, and also to the Buckeye and Bilgram valve gears, are substantially 
the same as those previously published (now largely inaccessible) by 
Mr. Bilgram. 



104 



SLIDE VALVE GEARS. 



valves open and close their ports with the same edge, i.e., 
in opening the port the valve draws to one side, and in 
closing it resumes the previous position. This cut-off 
valve, however, opens and closes the port by the port 
in the valve passing bodily across the port in the seat, 
the opening being done by one edge, and the closing 
by the other. Further, the same ports serve for both 
ends of the cylinder ; the valve ports passing over the 
seat ports in one direction for one end of the cylinder, 
and in the opposite direction for the other end. 

It will be seen from Fig. 62 that the cut-off valve 




/ . 

1 ( 


7 \ 


\ 


JV / 

/ 
/ 



Fig. 63 



Fig. 64 



has negative lap, since the ports are open when the 
valve stands at its central position. The width of port 
in the valve may equal or exceed the width of port in 
the seat. In the former case, the negative lap is equal 
to the width of port ; in the latter, to the distance a of 
Fig. 63. The location of the eccentrics is shown in Fig. 
64, d being the main and d f the cut-off ; 8 being the ad- 
vance angle of the former, and 8' of the latter. The 
centres of the lap circles Q and Q\ Fig. 65, are found in 



THE GONZENBACH VALVE GEAR. 



105 



the usual way, by laying off the angles 8 and 8' up- 
ward from the horizontal centre line. The effect of 
the three ported valve being equivalent to a valve with 
a single port of three times the width and travel, the 
throw of the cut-off eccentric is in the diagram in- 




Fig. 65 

creased to three times that shown in Fig. 64, and the 
lap circle is likewise drawn, with a radius three times 
the actual negative lap for each port. Starting at 
crank position A, it is clear that the main valve is 
open by the amount of its lead. The cut-off valve is 
at a distance Qa from its central position, which being 



J06 SLIDE VALVE GEARS. 

less than the negative lap, the cut-off ports are open, — 
a fact which is also shown by the dotted (negative) lap 
circle going below the horizontal centre line. As the 
crank rises, the port opens more widely, up to position 

B. In the original discussion of the Bilgram diagram 
it appeared that when the crank passed through Q the 
valve stood central upon its seat. In that position the 
ports of the present valve stand wide open, — as is 
apparent from the plan of the valve and the present 
diagram alike. Passing crank position B, the valve 
begins to close the port, not by returning toward its 
former position as with previous valves, but bypassing 
on to the other side of its centre line, — as is indicated 
in the present diagram, by the perpendicular from Q f 
falling upon the opposite side of the crank. 

The closure is completed and cut-off takes place at 

C, which is indicated in the usual manner. From this 
point expansion goes on in the cylinder and lower chest 
together, until crank position D is reached, where the 
main valve closes its port. As has been stated, the ex- 
pansion is varied by changing the angular advance of 
the cut-off eccentric. If 8' of Fig. 64 be increased, Q 
of Fig. 65 will be lowered toward the centre line and 
the cut-off position C of the crank will be shifted to an 
earlier part of the stroke. This change in the cut-off 
will be accompanied by an earlier and earlier admission 
from the upper to the lower steam chest, as will be 
shown by the large lap circle having a larger and larger 
segment below the horizontal centre line. Crank posi- 
tion D extended backward gives the position at which 
the main valve cuts off the steam on the previous stroke, 
and it is clear that the cut-off eccentric might be ad- 




THE GONZENBACH VALVE GEAR. 107 

vanced so far that the admission from the upper to the 
lower chest would occur before the main valve had 
closed its port in the previous stroke ; i.e., in advanc- 
ing the eccentric to obtain an early cut-off the result 
would be to give a second admission of steam at the 
latter end of the expansion. This feature limits the 
range of variation to the expansion which this gear can 
give. The only way to provide a shorter cut-off is to 
increase the lap of the main valve, since this carries 
crank position D backward, and allows the cut-off lap 
circle to be carried farther back before interfering with 
the main valve. 

The principles of this valve, and of the application 
of the diagram to it, can be fixed in the mind by fol- 
lowing the solution of 

Problem VII. A Gonzenbach valve gear is to be 
constructed with a maximum cut-off of f stroke. The 
greatest port opening to steam of the main valve is to 
be i\ n . Since there is nothing to prevent liberality in 
this respect, the cut-off ports will number three, each 
one inch wide in valve and seat alike. Required the 
shortest possible cut-off, and the positions of the cut- 
off eccentric for the earliest and latest cut-off. 

In Fig. 66 the centre Q of the main valve lap 
circle is found in the usual manner. Lead position 
A and maximum cut-off position B are then drawn. 
At the latest cut-off the cut-off valve lap circle must 
be tangent to A and B, and its radius being three 
inches (three times the port opening), it is easily drawn, 
giving Q f the position of cut-off eccentric for latest cut- 
off. Extending B downward and finding Q" such as 
to make the cut-off lap circle tangent to B extended, 



io8 



SLIDE VALVE GEARS. 



determines crank position C, the earliest cut-off prac- 
ticable with the dimensions given, and also the range 
of movement Q to Q" of the cut-off eccentric. 

It has been shown that the range of cut-off with this 
gear is somewhat limited. Another defect of the ar- 
rangement is the large volume of the lower chest, which 
.^creases the clearance space during expansion. The 



Xq; 







Fig. 66 



object of a separate cut-off valve is to introduce early 
cut-off, and it is in these early cut-offs that the effect 
of this increased clearance is greatest, making a serious 
discrepancy between the " real " and " apparent" ex- 
pansion. For these reasons, together with the inac- 
cessibility of the lower valve, the plan has largely fallen 
into disuse. 



THE MEYER VALVE GEAR, 



109 



THE MEYER VALVE GEAR. 

In this gear, which has been very extensively used, 
a separate valve is used for the sole purpose of cutting 
off, as in the last example. The general arrangement 
of the valves is shown in Fig. 67, from which it will be 
seen by reference to the dotted lines that the main valve 
is essentially a plain valve of the usual type, with the 
addition of a bridge at each end to form a port through 




Fig. 67 

The Meyer Valve. 

it, and planed upon its back to form a seat for the cut- 
off valves. These cut-off valves are driven by a sepa- 
rate eccentric, and, as shown, the cut-off valve rod con- 
tains a right and a left hand screw upon which the 
valves are threaded. The valve rod has a hand wheel 
upon it, and its connection with the eccentric rod is 
such as to permit its being rotated at will by means of 
the hand wheel. This rotation increases or decreases 
the distance apart of the valves, and thereby changes 
their lap and the point of cutting off. An index is at- 
tached, which, moving over a graduated scale, shows at 
a glance the position of the valves upon the stem and 



!I0 SLIDE VALVE GEARS. 

the degree of expansion. Occasionally this rotation of 
the valve rod has been connected to the governor, but 
the extent of the movement required and the friction 
incident to the mechanism are so great as to render 
such a plan a questionable success. Unlike the pre- 
vious gear, the angular location of the cut-off eccentric 
is not a matter requiring exactness. In the older prac- 
tice it was customary to place that eccentric exactly 
opposite the crank, or, since that gave the same motion, 
to connect the valve rod to the cross-head by means of a 
lever. This plan is still followed in marine, hoisting, and 
other engines which are to turn in both directions, since 
the motion of the cut-off valves is then correct for both 
forward and backward rotation. In present practice 
the cut-off eccentric of stationary engines is not usu- 
ally placed so far in advance of the main eccentric. A 
common location is forty five degrees in advance. The 
effect of this is to require a smaller movement for a 
given change of the expansion. To offset this advan- 
tage, it reduces somewhat the width of port opening 
given by the cut-off valve and the speed of cutting off. 
The application of the Bilgram diagram to this gear 
is shown in Fig. 68. The locations of the eccentrics 
are shown at d and d\ the throw of the latter exceed- 
ing that of the former, as is customary in practice. It 
will be understood at the outset that since the lap of 
the cut-off valve is changed to vary the point of cutting 
off, a number of cut-off lap circles will appear in the 
diagram. Some of these will represent positive and 
some negative lap, and the determination of the proper 
lap for different expansions is one of the leading points 
to be determined from the diagram. Since the seat of 



THE MEYER VALVE GEAR. 



Ill 



the cut-off valves is upon the back of the main valve, it 
is clear that the diagram must show the position of the 
former in relation to the latter. Beginning with crank 




\> 



/ / 


/ / 


/ / 


/ / 


/ / 


/ / 


/ / 


/ 


/ 


s 


<s 



Fig. 68 



position A, it is clear that the main valve is advanced 
to the right of its mid position by the distance Qa, and 
the cut-off valve by the distance Q'a. The cut-off valve 



112 SLIDE VALVE GEARS. 

is therefore removed from its mid position a distance 
Qa" greater than the main valve. If it is desired that 
the cut-off shall take place with the crank at A, there 
must be a lap given to the cut-off valve equal to Qa h ' . 
Hence the lap circle /'. Similarly for crank position B 
the main valve is at a distance Qb and the cut-off Q'b' 
from the central position. The displacement of the 
main valve is here the greatest by Q'b", and if the cut-off 
valve had a lap of zero the main valve port would still be 
covered by the distance Q'b". Therefore, if the cut-off 
is to occur at this position of the crank, the cut-off valve 
must have a negative lap equal to Q\ b n '. Similarly the 
value of the lap required for any cut-off may be found. 
If the range of cut off is to be from zero to that given 
by the main valve, the positive lap required for the 
former and the negative lap for the latter is easily found, 
and the sum of the two amounts will give the total move- 
ment of each valve on the stem to accomplish the required 
range. The tangents drawn from point Q to the various 
lap circles, and the perpendiculars dropped to them 
from the point Q\ form precisely the same construction 
from Q as a centre that the diagram for the plain valve 
did from O as a centre, and these lines with the lap 
circles give the relations of the two valves to one an- 
other precisely as though the main were a fixed seat 
for the cut-off valve. As in Fig. 15, the distance Oc 
represented the velocity of a plain valve at the moment 
of cutting off, so in Fig. 68 the distances Qa", Qb" repre- 
sent the velocity of the cut-off valve relative to the main 
valve at the same moment. In the figure it will be seen 
that this velocity is somewhat less than the correspond- 
ing velocity for the maximum cut-off by the main valve, 



THE MEYER VALVE GEAR. 113 

and in fact a somewhat sluggish cut-off is a characteristic 
of this valve gear. The only method of quickening this 
velocity is to increase the distance between Q and Q by 
increasing the throw or angular advance of the cut off 
eccentric. This, however, increases the diameters of 
the lap circles, and the distances which the valves must 
be moved on the stem, together with the length of steam- 
chest to permit the increased movement. If the full 
range of expansion is not required, the entire move 
ment on the stem is available for the limited range, and 
this can be put to good use by increasing the quickness 
of the cutting off ; but generally in practice it is neces- 
sary to adjust the conflicting requirements to one an- 
other with a view to securing the best compromise 
possible. 

The greatest distance apart of the centres of the main 
and cut-off valves, or in other words the half travel of 
the cut-off relative to the main valve, is the distance 
QQ '. Should the cut-off plates be brought so near 
together that the negative lap equalled this distance 
QQ\ the cut-off valve would close the main valve port 
for an instant and immediately reopen it. Should this 
happen before the final cut-off by the main valve, it 
would give a readmission of steam. To determine if 
this is possible, strike the negative lap circle in ques- 
tion with radius QQ'. Draw its tangent c through Q 
and a crank line D parallel to the tangent. This crank 
line D comes well within the main valve lap circle, indi- 
cating that the latest possible cut-off by the cut-off valve 
at which the momentary closure occurs takes place after 
the closure of the port by the main valve. Had the line 
D come tangent to the lap-circle it would have indicat- 



ii4 



SLIDE VALVE GEARS. 



ed that the momentary closure of the main valve port 
would have occurred just at the closure of the port by 
the main valve ; and had it fallen without the lap circle, 
as in Fig. 69, it would have indicated that some of the 
later grades of expansion would have been accompa- 

,D 







Fig. 69 

nied with readmission. This is of but little moment, 
as, unlike the previous gear, it affects the late and not 
the early cut-offs ; but it can be easily avoided. Thus 
in Fig. 69, lines C and D being parallel, QQ\ which is 
perpendicular to C> is also perpendicular to D. If the 



THE MEYER VALVE GEAR. 



"5 



position of Q be altered to Q f , such that QQ" is per- 
pendicular to E, it is clear that D and E will coincide, 
the limiting condition will have been reached, and if 




Fig. 70 

the centre of the cut-off lap circles be located slightly 
to the right of Q" , no possible readmission can occur. 
One point requiring attention remains. It is clear 



Il6 SLIDE VALVE GEARS. 

that were the cut-off plates quite narrow, they might 
when screwed well apart pass entirely over the main 
valve ports and readmit steam by their back edges, and 
the width must plainly be made great enough to pre- 
vent this. In Fig. 70 place the crank at the dead-point 
position A, and determine the lap necessary for cut-off 
at that extreme position. The valves are located at dis- 
tances Qa and Q'a' from their mid positions, and Q'a" is 
the radius of the required lap circle. As the crank 
mounts upward Qa lengthens and Q'a' shortens, until at 
crank position B parallel to QQ\ Qa and Q'a are equal. 
Beyond B, Qa exceeds Q'a', until at C, Q'a' vanishes. 
Beyond C, Q'a' falls upon the rear side of the crank, and 
at D, Q'a' becomes Q'd'. At this point the distance 
apart of the centres of the valves is Q'd' plus Qd. In 
other words, that distance has diminished from Q'a" to 
zero, and increased again in the opposite direction to 
Qd plus Q'd'. With the crank at A the edge of the 
cut-off plate just closed the port, and at D it will have 
closed the port by a distance Q'a" plus Q'd' plus Qd; 
and the width of the plate must equal this distance, 
plus the width of the main valve port, plus an allow- 
ance for tightness — say \". 

THE BUCKEYE VALVE GEAR. 

This exceedingly ingenious valve gear is in one 
sense a combination of the two preceding. To the 
small clearance and mechanical capabilities of the Meyer 
valve it unites the turning eccentric of the Gonzenbach 
with its convenient attachment to the shaft governor."* 

*The Buckeye was the pioneer shaft-governor engine. 



THE BUCKEYE VALVE GEAR. 



117 



At the same time it is not limited in range as is the 
Gonzenbach, and it has a sharper cut-off than either 
one. Balancing and other features of the valve dis- 
guise its relationships somewhat, but discussion of these 
features is beyond the scope of the present work. The 



^ 



t^W^w^^ 




Fig. 71 

The Buckeye Valve. 

construction of the valve, so far as its action on the 
ports is concerned, is shown in Fig. 71, from which it 
will be seen that it takes steam from within its box-like 
form, and exhausts by its ends into what with other 
valves is commonly the steam-chest. The cut-off 
valves are similar to those of the Meyer system, ex- 
cept that they are secured immovably upon the rod. 




e b 

Fig. 72 

Fig. 72 is an ideal view of the same valve with a diagram 
of the eccentrics. The position of the crank being 
at A, the main eccentric, by reason of the valve ex-! 
hausting by its outside edges, is at d. The main 
eccentric and valve rods are connected to a rocker 



Il8 SLIDE VALVE GEARS, 

pivoted at b. This rocker does not change the motion 
of the main eccentric in transmitting it to the valve. 
The cut-off eccentric and valve rods are also connected 
to a rocker, the former at c and the latter at e. This 
rocker is pivoted at f, which pivot is carried by the 
main rocker. It is clear that the motion which the 
cut off eccentric rod imparts to the lower end of its 
rocker is, if the eccentric be properly set, precisely the 
same as that required for a Gonzenbach cut-off valve, 
having its seat in line with the eccentric rod. But the 
distance be always equals eg, or, in other words, the 
motion of the upper end of the cut-off rocker relative 
to the main rocker is the same as that of the lower end 
relative to a fixed valve seat. That is, the motion of 
the cut-off valve relative to the main valve is the same 
as that of the Gonzenbach cut-off valve relative to its 
fixed seat. With the Gonzenbach gear a single set of 
ports through the cut-off valve-seat served for both ends 
of the cylinder, and it was shown that, in consequence, 
there was danger in the early grades of expansion of a 
readmission of steam before final closure of the port by 
the main valve. With the construction of the present 
gear this is avoided, and, properly proportioned, there 
can be no readmission in either the early or late grades. 
The exhaust taking place at the ends of the main valve 
locates the eccentric diametrically opposite from its 
usual position, and the cut-off rocker does the same for 
the cut-off eccentric. The angular position of the cut- 
off eccentric rod also moves the cut-off eccentric from 
the positions shown in Fig. 73 by the same angle. 
Since the action of the cut-off valve is essentially the 
same as in the Gonzenbach gear, it may be represented 



THE BUCKEYE VALVE GEAR. 



119 



by essentially the same diagram as in Fig. 73. Q is as 
usual the centre of the main valve lap circles and Q ', 
Q", Q!" of the cut-off (negative) lap circle for different 
points of cut-off, Q' being the position for cut-off at 




zero, Q" for latest cut-off, i.e., at the main valve closure, 
and (J" tor any desired crank position A. The open- 
ing of the ports by the cut off valves is in this instance 
oMittle moment, since it occurs during the previous 
stroke, when the admission port for the end of the 
cylinder under consideration is out of action. 



120 



SLIDE VALVE GEARS. 



THE STRAIGHT LINE INDEPENDENT CUT-OFF GEAR. 

Fig. 74 is a horizontal section of a steam cylinder 
fitted with the above valves, the bottom of the figure 




\V\VV\^^\V\^^^^^ 



showing the steam and the top the exhaust valve. The 
two are of similar construction, both being fitted with 



STRAIGHT LINE INDEPENDENT CUT-OFF GEAR. 121 



relief plates and multiple ports, and both acting by 
their outside edges. They differ chiefly in that the 
exhaust valve is driven by a fixed, and the steam valve 
by a swinging eccentric. The Bilgram diagram as ap- 
plied to the gear consists of the diagram already 

A B 




Fig. 75 



familiar for the swinging eccentric gear, but with the 
exhaust lap circle occupying a fixed position instead of 
the moving one of the usual swinging eccentric gear. 
Contrary to all previous practice with independent 
valves, this engine is arranged for positive lead in the 



122 SLIDE VALVE GEARS. 

late and negative in the early cut-offs. The object of 
this is as follows : It is generally understood that com- 
pression does not begin to bring the piston to rest until 
the pressure on the compression side exceeds that on 
the expansion side of the piston. With an early cut- 
off this state of affairs occurs at some distance from the 
end of the stroke, but at later cut-off the expansion 
curve is higher and the compression curve does not 
rise so soon to equal it. Hence the effect of the com- 
pression in bringing the parts to rest is lessened at late 
cut-off, and to make up for the deficiency a prominent 
lead is given. 

The application of the Bilgram diagram is shown in 
Fig. 75, in which Q is the centre of the steam valve lap 
circle for greatest throw, cut-off at B ; Q is the fixed 
centre of the exhaust lap circle, and Q" the centre of 
the steam circle with the eccentric shifted for cut-off at 
A, the path of the eccentric centre being QQ" . It will 
be observed that for cut-off at B the lead is positive 
and at A negative. The fixed position for compression 
is C, and for release D. 

THE BILGRAM VALVE GEAR/ 

This gear has been designed to provide a more rapid 
cutting off than the Gonzenbach or Meyer gear. The 
following description is from Mr. Bilgram's book on 
this subject (now out of print): 

Both valves are operated by one single eccentric/, 
Fig. 76 ; the main valve directly by the eccentric rod, 
and the cut-off valve through a peculiar mechanism, 
consisting of four members ; viz. : the link, the rocker, 



THE BILGRAM VALVE GEAR. 



123 




KA 



J] 




Fig., 76 



124 SLIDE VALVE GEARS. 

the cut-off rod, and the adjustment lever. The link 
AB being jointed by the pin A to the eccentric rod, 
imparts to the rocker a rocking motion on its fulcrum 
F. The rocker is of a peculiar shape, as shown de- 
tached in the cut, but it virtually represents a bell crank 
(or angular lever) having an angle BFC of about 50 , 
the arm CF of which is about twice as long as the arm 
BF. To the extreme end C of this rocker is jointed 
the cut-off rod, by which the cut-off valve is moved. 
For the purpose of changing the degree of expansion 
the fulcrum F of the rocker can be moved in a circular 
arc, being attached to the end of the adjustment lever 
GF, whose fulcrum G is a fixed point. 

The study of this gear will consist in the investiga- 
tion of the movement of the cut-off valve for several 
positions of the adjustment lever. In every case we 
shall proceed from the neutral position of the rocker 
(found by transferring the eccentric rod to the centre 
of the crank shaft), remembering that the movement of 
the mechanism will be symmetrical to both sides of this 
position. Besides, we shall as usuah neglect all com- 
plicating influences resulting from the angularity of 
the several members ; and besides, we shall assume the 
movement of the pin A to be strictly circular and co- 
incident with the movement of the eccentric /. 

At first we move the adjustment lever until the line 
CF of the rocker assumes a vertical position (see Fig. 
77), the theory for this position being the least compli- 
cated. When the mechanism is in operation, the pin 
A will move in a circle, and hence the points B and C 
will move in the arcs b'b" and c'c" . For the latter arc 
we shall substitute the chord to simplify the theory. 



THE BILGRAM VALVE GEAR. 



125 



When the crank is on its centre, the pin A will occupy 
the position A° corresponding to the position of the 
eccentric I, and since the link AB represents, as it 
were, the eccentric rod for the cut-off gear, we can 
measure the angle of advance 6° = YAA° by drawing 
AY dX right angles to BA. The angle CFB being 50 



K-^ 



<# — v 

/ 
/ 







X 






Fig. 77 

and AB being at right angles with FB, or approximately 
so, it is evident that the angle YAA° = 6° exceeds 
the angle of advance of the eccentric I by 50 . Owing 
to the dimensions of the rocker, the travel of the point 
C y and consequently also the travel of the cut-off valve, 
equals double the travel of the main valve ; and hence 
we can find the ideal eccentric i° of the movement of 
the cut-off valve for the considered grade by advancing 
the line 01 through an angle of 50 and doubling its 
length. 



126 SLIDE VALVE GEARS. 

Next we move the fulcrum F towards the right to 
F r to change the grade, and denote the angular change 
of the rocker by the Greek letter /?. The correspond- 
ing angular change of the link AB is practically the 
same, and the angular advance is consequently farther 
increased by this angle. We can therefore draw the 
line Oi'y but we have yet to find its length. The move- 
ment d'd" of the pin C of the rocker is doubtless the 
same as it was before ; but being inclined, it is only its 
horizontal component d ' d° that is transmitted to the 
valve, and the throw Oi' of the ideal eccentric for this 
grade will be less than Ot°. The necessary reduction 
can be made by drawing the line i °i f at right angles to 
0i\ which will be understood when we consider the 
similarity of the triangles Oi'i° and d'd°d n . 

In moving the fulcrum F of the rocker in the oppo- 
site direction we would have found the ideal eccentric 
i", and other positions of the fulcrum F would furnish 
more points of the locus of ideal eccentrics. The angle 
i°i r being a right one, it will ^easily be understood that 
all the ideal eccentrics will be located in a circle of 
which the line Oi° is a diameter. 

These results relate to the absolute movement of the 
valve, and to find the ideal eccentrics for the relative 
movement we move the locus in the direction of and 
through a distance equal to 10. Having thus deter- 
mined the locus/yy" of the relative movement, we can 
draw the valve diagram, Fig. 78, in the usual manner. 

This diagram now shows that the cut-off can be ad- 
justed to any point between the crank angles OA and 
OF as the angular adjustment of the rocker is not lim- 
ited. It shows, moreover, that this valve gear is distin- 






THE BILGRAM VALVE GEAR. 



127 



guished by the decided rapidity in cutting off. The 
closure of the steam passages is very sharp for all grades 
cutting-off before the half stroke ; for a later cut-off 
however, this rapidity will get less, until when cutting 
off at OE the rapidity of the cutting off of the cut-off, 
valve will about equal that of the main valve. 




Fig. 78 

The rapidity of the late cut-offs can be improved, if 
desired, by making the arm CFoi the rocker more than 
double the length of the arm BF, whereby the line 0i° 
will be lengthened, and consequently the locus circle will 
be enlarged. This change entails an increase of the ab- 
solute movement of the cut-off valve above twice the 
travel of the main valve. Another measure consists 



128 



SLIDE VALVE GEARS. 



in increasing the negative lap of the cut-off valve ; but it 
should never exceed the positive outside lap of the main 
valve. A reduction of the angle BFC of the rocker 
would likewise be efficient, but this reduction is at- 
tended by an increase of certain irregularities. 

The sharpness of the cut-off will in reality be slightly 
less than indicated in the diagram, from the fact that 
the movement of the pin A is not circular, as was as- 
sumed, but is more or less flattened. 

The proportioning of the mechanism requires some 




F ^F 



Fig. 79 



care, for on it depends largely the proper operations 
and regularity of the cut-off. To this end we draw the 
rocker BFC (Fig. 79) with the line CF in a vertical 
position and the line BF 'at an angle of 50 , and make 
the arm BF from three to four times the throw of the 
eccentric, and the arm CF twice as long. (The figures 



THE BILGRAM VALVE GEAR. 1 29 

given have been tested by a number of experiments.) 
Then we draw the link AB at right angles to BF and 
make it about ^ of the length of CF. The eccentric 
rod OP can next be shown in its neutral position, pass- 
ing through the end A of the link. The cut-off rod 
CP° can likewise be shown. 

To find the length and position of the adjustment 
lever GF, it is necessary to make a model of thin wood 
or veneer, consisting of the eccentric rod, the link, the 
rocker, and the cut-off rod. Next we draw the orbit of 
the eccentric, and on it the exact position of the eccen- 
tric, say for every one sixth of the stroke of the piston, 
which may be done in the following way, identifying 
the eccentric path with the path of the crank pin : 

We divide the diameter of the orbit passing through 
the initial position of the eccentric / in six equal parts, 
and draw the projection arcs of the proper radius 
through those points as shown. The next thing to be 
done is to attach the model to the drawing by joining 
the parts properly together with pins or thumb tacks, 
and fastening the ends P and P° of the rods to two 
slides representing the valves. The right end of the 
eccentric rod may be provided with a needle point 
which at first we put in the centre 0, when we set the 
rocker directly over the position shown in the drawing, 
and mark the relative position of the two slides repre- 
senting the valves. Then we make two additional 
marks on one of them, at a distance equal to the as- 
sumed negative lap of the cut-off valve, to show the 
relative position for the cutting off on either side. 
Suppose now we desire to find the proper position of 
the rocker for cutting off at the point 1. To this end 



130 SLIDE VALVE GEARS. 

we set the needle point of the eccentric rod in the point 
1 of the fore stroke, and fix the valves for cutting off 
at the proper side, when we will find that the end F oi 
the rocker cannot be moved but in a certain curve. 
This curve we mark on the drawing by setting a needle 
point into the rocker and making a slight scratch on 
the paper. Thereupon we attach the eccentric to the 
point 1/ of the return stroke, fix the cut-off valve to the 
point of closure of the other passage of the main valve, 
and mark another curve by the point F of the rocker. 
The juncture F r of the curves must of necessity be the 
exact position of the fulcrum of the rocker when we de. 
sire to cut off at one sixth of the stroke. In this way 
we can find the required position of the fulcrum for all 
the other grades, which will be found to form a curve. 
By substituting a circular arc for this curve, osculat- 
ing as closely as possible, we obtain the location and 
length of the adjustment lever GF. An arc can gener- 
ally be found to agree with the constructed curve with 
an almost absolute precision ; and hence it will be seen 
that this valve gear will admit of a practically perfect 
equalization of the difference between fore and return 
stroke. 



PART IV. 

THE SLIDE VALVE WITH LINK 
MOTION. 



The Slide Valve with Link Motion. 



APPLICABILITY OF THE LINK MOTION TO LOCOMOTIVE 
CONDITIONS. 

Probably no conspicuously successful mechanical 
device has ever been assailed so persistently as the lo- 
comotive link motion. The steam distribution which 
it gives is so unlike what is considered best in station- 
ary practice, and so like what is considered bad in that 
practice, that many engineers have regarded it almost 
with contempt as a device whose only redeeming virtue 
lay in the fact that it kept going. It is altogether 
probable, however, that these opinions are mistaken 
ones and that the link motion, comes little short of be- 
ing all that can be desired for a locomotive valve mo- 
tion. The locomotive works under conditions peculiar 
to itself; it must in consequence be studied by itself, 
and conclusions based upon experience with stationary 
engines have little or no applicability to it. It will be 
shown that the action of the link motion on the move- 
ment of the valve and the distribution of the steam, is 
essentially the same as that of the shifting eccentric, 
with, however, a still more restricted port opening, 
133 



134 LINK MOTION AND LOCOMOTIVE CONDITIONS. 

and.it is to the restricted port opening, the early re- 
lease and the heavy compression that the criticisms 
have been directed. In replying to these criticisms, 
the advocates of the link motion point to the well- 
known fact that an extreme degree of expansion in one 
cylinder is not conducive to economy, but the reverse, 
and they claim that the mean effective pressure re- 
quired by a passenger locomotive at speed is so small, 
that if it were to be obtained by a steam distribution 
analogous to that given by the Corliss gear, the cut- 
off would be so early as to have passed the economical 
point, and that under such conditions, partial throt- 
tling, with its consequent superheating, is better than 
cut-off without throttling. The heavy compression, 
so far from being a defect, considered purely as a fea- 
ture of the steam distribution, is pointed out to be 
here a positive advantage, as its effect is to reduce the 
cylinder capacity and thereby introduce a later cut-off 
than would otherwise be required. Moreover, apart 
from such considerations, the easy cushion due to a 
long compression is considered a mechanical necessity, 
to quietly absorb the momentum of the parts at speed, 
while the early release due to notching up the link is 
exactly adapted to the conditions, inasmuch as, when 
starting with the link in full gear, the speed is slow 
and the release is late, as it should be, while at speed, 
when increased exhaust lead is required to compensate 
for the increased speed and provide sufficient time to 
enable the steam to escape, it is provided by the draw- 
ing of the link toward the mid gear which accompanies 
increase of speed. In freight engines the mean effec- 
tive pressure is greater and the cut-off later than in 



SLIDE VALVE GEARS. 1 35 

passenger locomotives. The port opening is conse- 
quently larger and the compression less, so that there 
is little to criticise in these respects from the stand- 
point of the critics of the link motion, who have in 
fact mainly directed their criticisms to passenger loco- 
motives. The cylinder problem of a locomotive is in 
fact entirely different from that of a stationary engine. 
With the latter, the problem is to determine the size 
of the cylinder and the distribution of the steam to 
drive economically a given load at a given speed. 
With locomotives, the cylinder is made of a size which 
will start the heaviest train which the adhesion of the 
locomotive will permit, and the problem then is to uti- 
lize that cylinder to the best advantage at a greatly 
increased speed, but under a greatly reduced mean 
effective pressure. 

It will thus be seen that the properties of the link 
motion are fairly in the direction of the requirements, 
and while notching up the link may not give the 
changes desired to the exact degree which refined con- 
siderations might dictate, it does give them in the 
right direction and probably as nearly correctly in de- 
gree as the varied conditions would permit, even with 
the most elaborate valve gear. 

The difficulty of the restricted port opening has no 
doubt been unduly magnified. There can be no doubt 
that many cases of loss of pressure in the cylinders of 
stationary engines have been attributed to the small 
port opening which belonged to the long steam pipes, 
for it is an undoubted fact that a mere diaphragm in a 
steam passage, which is what the port opening amounts 
to, does not give the obstruction to the flow of steam 



I36 LINK MO TIONS A ND L CO MO TI VE CONDITIONS, 

that would be expected from its area. Moreover, the 
common rules for port opening are based on experi- 
ments with engines having a late cut-off, and there 
can be no doubt that with an early cut-off and the ac- 
companying comparatively low velocity of piston up to 




American Machinist 



Fig. 80. Speed 55 miles per hour. 

the point of cut-off, the port area required is not as 
large as when the cut-off is late. The indicator cards 
given in Fig. 80* show clearly enough that the loss 
in pressure at admission is much less than would be 
expected from the small port area and certainly show 
little need of a new valve gear to reduce it. Some 
may object that these cards are better than the average 
and so are not fairly representative of the work of the 
link motion. Be this as it may, they show what it can 
be made to do. Many, whose opinions are entitled 
to every respect, would say that they show too little 
throttling for the best economy. There can be no 



* By C. H. Quereau, General Foreman Motive Power, Burlington 
& Missouri River R. R., in Nebraska, in Proceedings Western Rail- 
way Club, March, '97. 



SLIDE VALVE GEARS. 



137 



doubt that many cases of low steam line in locomo- 
tives are due to defective mechanical features of the 
valve gear and not to its geometrical properties. Fig. 
81* gives indicator cards which show the effects of 
spring in the crooked eccentric rods which are often 
used on consolidation and 10-wheel engines. The en- 
gine from which these cards were taken had such rods, 




.American Machinist 



Valves well lubricated 



Deficient lubrication, 



Fig. 81 



and the differences shown between the two pairs of 
cards were brought about by changing the lubrication 
of the valve — the spring of the rods being largely re- 
moved w r hen the oil supply was sufficient. 

THE STATIONARY AND SHIFTING LINK MOTIONS 
COMPARED. 

It will be shown that the shifting link motion gives 
a varying lead for different rates of expansion. This 
has been considered by many to be a serious defect of 



* By E. M. Heir, Asst.-Supt. Motive Power, Chicago & Northern 
Ry., in Proceedings Western Railway Club, March, '97. 



138 SLIDE VALVE GEARS. 

this gear, and some gears have been devised largely 
for the express purpose of overcoming it. It is, how- 
ever, probable that this supposed defect of the shifting 
link, like those of link motions generally, is, as a mat- 
ter of fact, a point of superiority. 

The variable speed under which locomotives operate 
must always be kept in mind in considering any feature 
of their steam distribution. It is certainly proper to 
provide a heavier cushion for high speed than for low. 
This all link motions do to a certain extent, by increas- 
ing the compression. In addition to this, the shifting 
link gives a further increase of*cushion by the increase 
of lead. It is at least as probable that this increased 
lead cushion is needed as it is that it is not, while the 
further fact that the increased lead gives so much in- 
creased port opening at short cut-off, is certainly in 
favor of the shifting link, unless that link gives a larger 
port opening than is needed, and this its warmest ad- 
vocates will scarcely claim. It is certainly difficult to 
see wherein an increase of lead with an increase of 
speed can be justly criticised. 

THE LINK MOTION AND THE SHIFTING ECCENTRIC 

COMPARED. 

The movement of a link driven by two eccentrics 
and hung in the usual manner is extraordinarily com- 
plex. These complexities arise from distortions of the 
motion which are introduced by the angular vibration 
of the eccentric rods and of the link itself, and by the 
rise and fall of the link due to its suspending stud be- 
ing guided in the arc of a circle. While these distor- 



LINK MO TION A ND SHIF TING E CCEN TRIC. I 3 9 

tions are present, they are small in magnitude and of 
little real importance in the preliminary inquiry, and 
by ignoring them the subject may be simplified and 
the movement studied with a degree of accuracy suf- 
ficient for all purposes. 

The effect upon the valve movement due to raising 
the link from the full gear position is essentially the 
same as that due to shifting a single eccentric across 
the shaft in the manner common to high-speed shaft- 
governor stationary engines, with the addition that by 
raising the link beyond the mid position the engine 
is reversed, while in shifting eccentric stationary en- 
gines, there being no occasion for reversal, the eccen- 
tric is not moved beyond the mid position. Were a 
shifting eccentric arranged to pass the mid position, 
such movement of the eccentric would reverse the en- 
gine and produce all the other effects of the link, and, 
in point of fact, locomotives have been fitted with 
such a valve gear. 

The first step in the study of the link motion is then 
properly a demonstration of the similarity of its move- 
ments with those of a single shifting eccentric. 

This may be done by the aid of Fig. 82*, in which, 
it is to be distinctly understood, the distortions already 
mentioned are ignored. Consequently the demonstra- 
tion is only approximate, but it is sufficiently accurate 
for the purpose ; in other words, the movements are 
not exactly as the demonstration would indicate though 

* Reversing the practice of the previous parts of this book, the 
cylinder will, in all figures of this part, be located to the right of the 
shaft. This is done to conform to the customary practice in loco- 
motive drawings of showing the right hand side of the locomotive. 



140 



SLIDE VALVE GEARS. 



they are very nearly so. The dotted circle gives the 
path of the eccentrics, the position of the forward ec- 
centric for the dead point position of the crank being 
at a, while that for the backward eccentric is at b. 
The shaft is supposed to have been turned forward 
until the forward eccentric has reached the point c and 
the backing eccentric the point d ; the corresponding 




position of the link, which is here represented by a 
straight line, being c d' . The line A' B' represents 
the position which the link would occupy if the cen- 
tres of the eccentrics were both placed at the centre 
of the shaft at O. This line is often called the neu- 
tral position of the link, although, in point of fact, the 
link, as a whole, never occupies it. With the eccen- 
trics at a b y the link would occupy a position parallel 
to this line A' B\ and every point of the link oscillates 
equally each side of this line, but only one point of 



LINK MOTION AND SHIFTING ECCENTRIC. 141 

the link is on the line at the same time, as the link always 
crosses it at an angle. The horizontal movements 
of the points c' and d' are assumed to be exactly the 
same as those of the eccentric centres c and d. That is 
to say, it is assumed that a point dropped vertically from 
c' to 'the centre line will travel upon that line exactly 
as will a corresponding point dropped from c, and that 
a point raised from d ! will travel as will one from d. 
It is in this assumption that the slight inaccuracy of 
the demonstration lies, the error of the assumption 
growing out of the angular inclination of the eccentric 
rods; but, as before stated, the error is slight and of 
small importance. Selecting a point as e upon the 

link such that, say, c e — and a corresponding 

4 

point e such that c e = ,it is required to show that 

4 
the horizontal movement of e' is the same as that of e ; 
or, in other words, that e' might be connected to e by 
a rod without changing the motion. It is obvious 
that 

and similarly that 

of=af, 

The division of the line c d' by e is in the same 
proportion as the division of c d by e, consequently It 
divides /' g' in the same proportion that h divides f g; 
that is, 

fk=fh'., 

subtracting O f from / h and its equal O' f from /' h\ 
gives us 

Ok=0h'. 



142 SLIDE VALVE GEARS. 

That is to say, the horizontal distance of c f from the 
central line A' B' is the same as that of e from A B. 
The same proof will hold for any angle of turning of 
the crank, and for any position of e and e\ 



THE STATIONARY LINK GIVES CONSTANT LEAD. 

The above discussion relates strictly to the station- 
ary or Gooch link in which the point of suspension is 
not changed in notching up, that being affected by the 
movement of a radius bar connected with the valve 
stem as shown in Fig. 83, which shows the same con- 
struction as Fig. 82, except that the link is curved con- 
vex toward the shaft, and a radius bar of a length 
equal to the radius of the link is added. The crank 
is shown in the two dead-point positions, one being 
given by a full line, and the other by a dotted line ; 
the corresponding positions of the other parts being 
shown by similar lines. The valve is shown open to 
its lead for the full-line position, and it is obvious that 
the radius bar may be swung through the entire arc of 
the link without disturbing the lead ; and the same 
would obviously be true of the dotted-line position. 
The feature of a constant lead is characteristic of the 
Gooch link, wherein it is similar to a shifting eccentric 
moved across the shaft in the straight line C D of 
Fig. 82*. 

* In view of its slight use in this country, an examination of the 
action of the Gooch link, due to the fact of the paths of its two ends 
not passing through the centre of the shaft, by which the virtual 
eccentric centres are not the same as the actual, seems uncalled for. 



SHIFTING LINK GIVES VARIABLE LEAD. 1 43 



THE SHIFTING LINK GIVES VARIABLE LEAD, 

With the shifting link motion the link itself is raised 
or lowered to reverse the engine or shorten the cut- 



00 




off. The nature of the movement of the valve is not 
thereby materially changed although an important dif- 



144 



SLIDE VALVE GEARS. 



ference is introduced in making the lead variable. 
The reason for this variation in the lead can be seen 



^*a 




-s s 



s 



from Fig. 84, which represents the shifting link as 
commonly applied to American locomotives. The 






SHIFTING LINK GIVES VARIABLE LEAD. I45 

crank is shown upon the forward centre, for which 
position of the crank the forward eccentric is at a and 
the backing eccentric at b y the forward eccentric rod 
being shown by a full line and the backing rod by a 
dotted line. In this position of the crank the valve 
has opened the port by the amount of the mid-gear 
lead. If now the backing eccentric be moved so that 
its centre coincides with that of the forward eccentric 
at a y and the link be dropped to the full gear position, 
the valve will take the full gear lead, and if the link 
arc has been struck from a as a centre, the link may be 
swung throughout its range without disturbing this full 
gear lead. If now the centre of the backing eccentric 
be brought back to its true position at b, the lower end 
of the link will be swung from d to d\ the link block 
will be pushed to the right from c to c' and the valve 
will be drawn to the left, thereby increasing the lead 
for the mid-gear. In other words, the full line valve 
sketch shows the full gear lead, while the dotted posi- 
tion shows the mid-gear lead. 

Fig. 85 shows the same arrangements with the crank 
turned to the back centre, the forward eccentric now 
occupying the position a and the backing eccentric the 
position b. It is evident as before that with the back- 
ing eccentric moved to coincide with the forward ec- 
centric at a, the link may be raised or lowered through- 
out its range without affecting the lead, but that 
replacing the backing eccentric to its true position, b 
will draw the lower end of the link to the left and in- 
crease the mid-gear lead as before. The proportions 
of these diagrams are purposely so chosen as to exag- 
gerate this action. In actual full-sized locomotives 



146 



SLIDE VALVE GEARS. 




having, say, 1-16 inch in the full gear, the lead in the 
mid-gear is increased to from \ to -| inch. 



LONG AND SHORT ECCENTRIC RODS. I47 

THE CORRECT RADIUS OF THE LINK. 

Figs. 84 and 85 also serve to show that the proper 
radius of the link is the length of the eccentric rod, 
plus such distance as there may be between the link 
arc and the eccentric rod pin — none here shown. 

If the link were struck with a smaller radius using 
the same length of rods the effect would be an increase 
in the mid-gear lead in Fig. 84, but a decrease in Fig. 
85, while if it were struck with a larger radius the effect 
would be to decrease it in Fig. 84 but to increase it in 
Fig. 85 ; that is, the effect of using any other radius 
than the one shown would be to make the mid-gear 
lead unequal for the two ends of the cylinder. It has 
been repeatedly suggested that the link could be 
curved in such a way as to compensate for the action 
of the rods in making the mid-gear lead greater than 
that for the full gear, and while it would of course be 
possible to find a curve for the link of very large radius 
such that the link block c, of Fig. 84, should not 
change its position for the forward centre as the link 
is raised or lowered, this would only produce a still 
larger mid-gear lead for the back centre as shown in 
Fig. 85. In other words, a link so arranged as to pro- 
duce a constant lead for all grades of expansion at one 
end of the cylinder would be at the expense of a still 
greater variation for the other end of the cylinder. 

LONG AND SHORT ECCENTRIC RODS. 

The effect of shortening the eccentric rods is to 
increase the difference between the full and mid-gear 



148 



SLIDE VALVE GEARS. 



leads, as will be seen by Fig. 86, which shows the 
same construction as that of Fig. 84, but drawn for 




3 
•i 









two lengths of rods. It will be seen at once that the 
distance between c" and c"' is much greater than that 



OPEN AND CROSSED RODS. 1 49 

between c and c' . This increase in the mid-gear lead 
with short rods accounts for the strong effort always 
made to use long eccentric rods, which in the case of 
consolidation and ten-wheeled engines has been car- 
ried so far as to carry the rods over the forward driv- 
ing axle at the expense of making them crooked. The 
spring of crooked rods is, however, so great as to lead 
to a defective valve action as has already been shown 
in Mr. Herr's cards given in Fig. 81, and the Schen- 
ectady Locomotive Works now make the eccentric 
rods in these engines much shorter, the rock shaft be- 
ing placed between the forward and the next following 
driver, instead of forward of the forward driver. This 
is done because experience shows the evils due to the 
increased mid-gear lead of short eccentric rods, to be 
less than those due to the spring of the crooked rods. 

OPEN AND CROSSED RODS. 

A link motion arranged as shown in Figs. 84 and 85, 
is said to have open rods, whereas with the rods ar- 
ranged as in Fig. 87 they are said to be crossed. 
These rods will be seen also to be crossed in Fig. 85, 
so that the term is not altogether fortunate. It is to 
be understood, however, that by the term open rods, 
as describing a link motion, is meant that the rods are 
uncrossed when the eccentric centres lie between the 
link and the vertical centre line of the shaft, or, in 
other words, that the forward eccentric connects with 
the upper end of the link. By diagrams similar to 
Figs. 84 and 85 it could be shown that the effect of 
crossed rods is to give a decreasing lead as the cut-off 



i5° 



SLIDE VALVE GEARS. 











Is 




1 ^^"^ 




1 ^ 

V 

\ 


1 
/ 

/ 



is shortened. Crossed rods are not, however, in actual 
use, and a detailed discussion of them seems uncalled 
for. 






THE BIL GRA M DIA GRA M. I 5 I 

THE BILGRAM DIAGRAM. 

The action of the Gooch link being thus closely ana- 
logous to that of the shifting eccentric, and the shift- 
ing link to the swinging eccentric, it follows that the 
Bilgram diagram as applied to these eccentric gears is 
also applicable to the link motion. Thus Fig. 47 re- 
presents the action of the Gooch link with constant 
lead, while Fig. 48 gives the action of the shifting link 
with open rods and increasing lead, and Fig. 49 applies 
to the shifting link with crossed rods and decreasing 
lead. In this connection, however, it should be ob- 
served that while the lead does not increase in Fig. 47, 
the lead angle does increase, and with it the distance 
through which the piston labors under the lead steam, 
from which it is plainly seen that a constant lead open- 
ing of the port for different cut-offs does not by any 
means imply a constant lead cushion to the piston, and 
that gears giving a constant lead do not differ so much 
in their effect from those giving an increasing lead, as 
is sometimes supposed. 

Comparison of Figs. 47 and 48 will also show that 
at early cut-offs the port opening to steam is materially 
greater with increasing than with constant lead, from 
which deductions favorable to the shifting eccentric 
have already been drawn. 

In stationary engines fitted with a shifting eccentric 
there is of course no occasion for reversal of the mo- 
tion, but if desired that could be accomplished by caus- 
ing the eccentric to swing past the point d° ol Fig. 48. 
Such action of the eccentric in backward motion is 
shown in Fig. 88, the position of the crank for lead, 



152 



SLIDE VALVE GEARS. 



cut-off, release, and compression being shown for two 
positions of the eccentric. Should the eccentric be 
swung to the point d° of Fig. 48, said point d° would 
belong to both lower and upper arcs and being located 




American Machinist 



Fig. 88. 

at the point where the direction of motion changes 
two lap circles could be drawn, as shown in Fig. 89. 
It will be seen in Fig. 89 that, with the eccentric in 
this position, the cut-off position for the forward mo- 
tion is the same as the lead position for the backward 






THE ACTION OF THE LINK, 



153 



motion and vice-versa, and that the greatest port open- 
ing is equal to the lead opening; and this represents 







^^"~ 





~^\ 




* 






x 




s 






\ 




s 






\ 




/ 


S'^JT 




*^>^ \ 




f 






\\ \ 


/ 










/ 
/ 

/ 

1 


/ 

/ 
/ 




i — .«-_- 


1 » \ \ 

A 1 \ \ 


i 
i 
i 


/ 
1 

I 


1 \ 


V^ 


1 1 i 


1 

i 


1 
\ 
\ 






i 


i 

\ 
\ 


\ 


\ S 






\ 
\ 


\ y 




^ 




\ 








\\ / f 


\ 




v \ 




1 \ / * 




\ 






y y / 




\ 






/ 










/ 




V 


s. 




s 

^ 






^^ 





** 








American Machinist 



Fig. 89. 

the action of an eccentric or of a link when placed in 
the mid-gear. 



THE ACTION OF THE LINK. 



The general similarity of the action of the link and 
shifting eccentric having been shown, it will be of 
service to examine the movement of the link more 



154 SLIDE VALVE GEARS. 

minutely. In this connection it should be remembered 
that when the valve admits or shuts off steam it is dis- 
placed from its middle position by an amount equal to 
its lap. This will be apparent from Fig. i, which is a 
cross-section of such a valve located centrally upon the 
valve seat. It will be seen that both ports are covered 
on the outside by the lap, and that to move the valve 
to the admission or cut-off position for the right-hand 
port involves a movement to the left equal to the lap, 
while to move it to the admission or cut-off position 
for the left-hand port, involves a similar movement to 
the right, and in all cases cut-off takes place with the 
centre of the valve approaching the centre of the seat. 

In Fig. 90 o is 'the central or neutral point of the 
movement of the lower rocker arm and pin, at which 
point the valve stands centrally over its seat. This 
point is found in the diagram by placing the link in the 
mid-gear and the crank on the two centres successively, 
these positions being shown in Fig. 94. In these po- 
sitions of the crank the valve and lower rock arm pin 
occupy the extreme points of their travel for the mid- 
gear and a point half way between the extreme points 
of the pin, that is half way between a and b of Fig. 94 
locates of Figs. 90 and 94. Measuring to the right 
and left of a distance equal to the lap (the two rock 
arms being supposed to be of equal length), locates 
points i and n, Fig. 90, at which the ports are opened 
or closed, according to the direction of the movement. 

The valve sketches above and to the right in Fig. 90 
show the valve in these positions, the upper sketch 
showing the valve in the act of cutting off steam for 
the rear port, while the lower sketch shows a similar 



THE ACTION OF THE LINK. I 5 5 

action on the forward port. The sketch shows the 
link in skeleton diagram suspended in the usual man- 
ner by a hanger which again is suspended from the re- 
verse shaft arm. It will be seen that this hanger is 
not attached to the link over the centre of the link arc, 
but at a considerable distance in the rear of this arc, 
and it will be seen at once from the diagram that 
the point i of the link at which it acts upon the link 
block for the forward port cut-off is farther removed 
from the centre t of the link arc than is the point ;/ at 
which it acts upon the block for the rear port cut-off. 
In other words, the link is nearer the full gear position 
for the forward port cut-off than it is for the rear port 
cut-off, in consequence of which the forward port cut- 
off is made later and the rear port cut-off earlier than 
they would be if the saddle stud were placed immedi- 
ately over the link arc. 

The positions shown in Fig. 90 may be traced through 
with advantage as follows : If the crank be placed 
upon the forward centre O A, the forward eccentric 
will occupy the position a and the backing eccentric 
the position b, while if the crank occupies the back 
centre O B, the forward eccentric will be at a and the 
backing eccentric at b' . If the cut-off is to be equal- 
ized at one-third stroke, points c d may be laid down 
such that A c and B d equal one-third of the stroke. 
Then with a radius equal to the length of connecting 
rod, arcs c A' and d B' may be drawn giving crank po- 
sition O A\ which the crank occupies at one-third stroke 
of the piston in the rearward motion, and O B\ which 
it occupies at one-third stroke of the piston in the for- 
ward motion. Taking the distance e f in the dividers 



156 SLIDE VALVE GEARS. 

and laying it down from a and b, point g is obtained, 
which the forward eccentric occupies, and point /z, 
which the backward eccentric occupies, when the crank 
is at O A f . These points locate the eccentric rod pins 
at g\ h' and give the link position shown in the full 
line, for cut-off at crank position O A '. Similarly by 
laying off j k from a! and b', we obtain point / for the 
forward eccentric and m for the backing eccentric when 
the crank is at O B\ These points again locate the 
link in the dotted position for cut-off at crank position 
O B f . It will be seen that if the reverse shaft arm / 
q be located as shown, so that the hanger swings 
equally each side of the vertical, points r s will occupy 
a horizontal straight line, and if the reverse shaft be so 
located that its arm is in the horizontal position when 
the link is raised to the mid-gear, it will be raised as 
much above the horizontal line for one-third cut-off in 
the backing motion as it is here in the forward motion, 
when r and s will again occupy a horizontal line above 
the centre line and the cut-off will be equalized for the 
backward motion as the diagram shows it to be for the 
forward motion, and it is in this way that the reverse 
shaft is located. It will be seen that this method of 
hanging the link introduces the element of slip by 
which the link rises and falls on the block. Formerly 
it was thought desirable to reduce this slip as much as 
possible, and even to be satisfied with a motion which 
was not perfectly equalized in order to accomplish this, 
but at the present time constructors do not seem to be 
afraid of considerable slip. 






ERRORS OF THE LINK MOTION. I 57 

ERRORS OF THE LINK IVfOTION. 

As locomotives are built, there are three sources of 
error which tend to make cut-off, release and compres- 
sion occur at different points in the stroke for the two 
ends of the cylinder. These sources of error, in the 
order of their importance, are, the offset of the eccen- 
tric rod pins back of the link arc, the angular vibration 
of the eccentric rods and the angular vibration of the 
connecting rod. To a certain extent the latter two 
compensate the first, but not entirely, and to complete 
the compensation the hanger stud is set back of the 
link arc. So far as I am aware, the importance of the 
first two sources of error has not before been recog- 
nized. 

All previous discussions of the link motion with 
which I am acquainted, proceed upon the assumption 
that the hanger stud is adjusted to correct the irregu- 
larities due to the connecting rod, although, in point 
of fact, the adjustment made is the direct opposite of 
what would be required if this were its purpose. 

If a link motion be laid down with the Scotch yoke 
connection between the piston rod and crank pin, 
which obviates the error due to the connecting rod, 
the offset of the saddle pin necessary to obtain an 
equalized cut-off will be found to be greater than if 
the connecting rod be introduced, and if a connecting 
rod be shortened, this offset will be found to diminish 
with each shortening of the rod, until, at some very 
short length, the stud will be placed over the link arc* 

* Mr. Harry Cornell, of Louisville, Ky., calls my attention to 
an article of his in the "Brotherhood of Locomotive Engineers' 



158 SLIDE VALVE GEARS, 

In other words, the connecting rod, instead of being a 
disturbing factor, as has heretofore been taught, is in 
reality a corrective factor, since it, to a certain extent, 
corrects other errors, and in so far as it corrects these 
errors it reduces the offset of the saddle stud, the re- 
maining offset being for the purpose of correcting the 
residual error due to the offset eccentric rod pins. 



THE ERROR DUE TO THE ANGULAR VIBRATION OF 
THE CONNECTING ROD. 

This error has already been examined at length in 
Part I. Considered as' a source of error, in connection 
with link motion, it is but one of three, and in import- 
ance the smallest of the three. As given in Part I the 
error was stated as though it existed in the position of 
the cross-head — the motion of the crank pin being 
taken as the starting point and assumed to be true. 
For the study of the link motion it will be more con- 
venient to reverse this proceedure, and to consider the 
motion of the cross-head as the starting point, the 
error being then in the position of the crank as com- 
pared with the position due to a Scotch yoke. Looked 
at in this way it is clear that during the rearward move- 
ment of the cross-head from a Fig. 91, the crank lags 
behind its correct position, while during its forward 
movement from b, the crank runs ahead of its correct 



Journal " for October, 1896, in which he points out that the offset 
of the saddle stud decreases with the length of the connecting rod. 
It does not appear, however, that Mr. Cornell went far enough to 
discover the real source of the error or the real purpose of the offset 



ANGULAR VIBRA TION OF CONNECTING ROD. 



159 



position — these errors existing at all points but being 
at a maximum at or near the half stroke. 

The study of the effect of this action upon the link 
is most easily made by separating it from the other 
errors, and as there is a similar error due to the angu- 
larity of the eccentric rods, the study of the connect- 
ing rod error requires that the eccentric rod errors be 
gotten rid of by assuming the horizontal movements 




Fig. 91. 



American Machinist 



of the eccentric rod pins in the link ends to be truly 
the same as those of the eccentric centres. This 
assumption of no angular swing on the part of the 
eccentric rods, involves the further assumption of a 
straight link. Similarly, the elimination of the error 
due to the offset eccentric rod pins, requires the loca- 
tion of these pins to be on the link centre line. Fig. 
92 has been made in accordance with these require- 
ments, and shows the link positions for the crank po- 
sitions of Fig. 90, with the errors due to the connect- 
ing rod included. 

These errors in the position of the crank are obvi- 
ously repeated in the eccentrics and link, that is for 



i6o 



SLIDE VALVE GEARS. 



the rearward movement of the piston, when the crank 
lags behind its proper position, the eccentrics and link 




* 

American Machinist 



Fig. 92. 



will do the same, and cut-off will not have occurred at 
the point desired. For the forward or return stroke 



ANGULAR VIBRATION OF CONNECTING ROD. l6l 

the conditions are reversed, the crank, eccentrics and 
link being ahead of their correct positions, and cut-off 



1 




, k j 


~7 


\ 




\ 




\ 




\ 




\ 




\ 




V ■* 




n\ o| 


fl 


>^y 






American Machinist. 



Fig. 93. 

having already occurred at the desired point of the 
stroke. This condition of things is shown in Fig. 92, 



I 62 SLIDE VALVE GEARS. 

in which the cut-off points i and n of Fig. 90 are re- 
peated. The arrows show the direction of the motion, 
and it will be apparent at once that the full line link 
has not reached the cut-off point, while the dotted line 
link has passed it. It is clear that these errors could 
be corrected by slightly raising the full line, and drop- 
ping the dotted line position, and to do this only re- 
quires that the link stud be placed outside the link 
centre line, as shown in Fig. 93, and this adjustment 
of the stud will be seen to be the exact reverse of that 
actually followed in locomotives — demonstrating the 
position here taken, that other errors override that due 
to the connecting rod. 

THE ERROR DUE TO THE ANGULAR VIBRATION OF 
THE ECCENTRIC RODS. 

It is apparent at first glance that the action between 
the eccentrics and link ends is in a sense similar to that 
between the crank and cross-head. There is, how- 
ever, an important difference. Reference to Fig. 91 
will recall the fact that with the connecting rod the 
error is zero at the centres and at its maximum near 
the quarter, but this is not the case with the eccentric 
rods, because the paths of the link ends do not pass 
through the centre of the shaft. Referring to Fig. 94, 
it will be seen that the average angle between the 
eccentric rods and the centre line is smallest in the full 
line position, and that this angle increases during the 
entire semi-revolution and becomes a maximum at the 
dotted line position. In other words, the distortion, 
instead of increasing to a maximum for 90 degrees of 



ANGULAR VIBRA TION OF ECCENTRIC ROD. 163 

rotation and then decreasing again, really increases to 
a maximum at 180 degrees of rotation. This increas- 
ing angle of the rods increases the movement of the 
link, and whereas the stroke of a cross-head is exactly 
twice the length of the crank, the movement of the 
link centre a b is materially more than the distance c 
d (in the case of this diagram nearly 50 per cent. more). 
Starting at b, the error in the position of the link cen- 
tre steadily increases during the movement toward a. 
The errors being greatest during the second quadrant 
of rotation, they increase the movement more during 
the second quadrant than the first. In other words, 
the movement of the link centre is greater during the 
second quadrant than the first. Consequently if a dia- 
gram like Fig. 95 be laid down it will be found that 
the first quadrant of movement from the full line posi- 
tion of Fig. 94 to that of Fig. 95 leaves the link cen- 
tre appreciably to the right of the neutral point 0, and 
similarly a quadrant of movement from the dotted line 
position of Fig. 94 to that of Fig. 95 will carry the 
link centre to the right beyond 0, and the same is true 
of any other angle of rotation. In other words, the 
movement of the link centre toward the left is too 
slow, while the movement to the right ij too fast. 
The rocker reverses these movements on the valve, 
leading to too slow a movement to the right with too 
late a cut-off on the forward port or rearward stroke, 
and too fast a movement to the left with too early a 
cut-off on the rear port or forward stroke. These ef- 
forts are obviously in the same direction as those due 
to the connecting rod error, and the two are, in fact, 
added together in an actual locomotive. The correc- 



164 



SLIDE VALVE GEARS. 



tion of this error obviously requires an adjustment of 
the saddle stud in the same direction as that made to 




American Machinist 



Fig. 96. 

correct the connecting rod error. Fig. 96 shows this 
in amount, this diagram having been constructed with 
the connecting rod error eliminated, and the offset of 






ANGULAR VIBRATION OF CONNECTING ROD. 165 

Fig. 96 will be seen to be greater than that of Fig. 93, 
for the connecting rod alone. Fig. 97 shows the off- 




American Machinitt 

Fig. 97. 

set necessary to correct the errors of both connecting 
and eccentric rods — the amount being approximately 
the sum of the offset of Figs. 93 and 96. 



1 66 SLIDE VALVE GEARS. 



THE ERROR DUE TO THE LOCATION OF THE ECCEN- 
TRIC ROD PINS BACK OF THE LINK ARC. 

In the previous study of the movement of the link, 
the eccentric rod pins were assumed to be located in 
the link arc, and in previous discussions of the subject 
it has been tacitly assumed that the errors introduced 
by setting these pins back of the arc are so small as to 
be negligible. This, however, is by no means the 
case, this error being, in fact, by far the most impor- 
tant of the three, over correcting, as it does, both the 
others, and resulting in finally locating the saddle stud 
inside the link arc, instead of outside, where the pre- 
vious errors alone would place it. This error, like the 
others, may be best studied by isolating it so far as 
possible, although it is not possible to separate it from 
the eccentric rod error, as will be seen. It is, how- 
ever, possible to separate it from the connecting-rod 
error. The nature of the error may be seen from Fig. 
98, which shows both forms of link, one having the 
eccentric rod pins located in the arc, and the other 
having these pins located three inches back of the arc, 
as is customary. The eccentric rods for the former 
link are, of course, three inches longer than for the 
latter. The saddle stud is located over the centre of 
the link arc, as is shown in the diagram, and the links 
are shown approximately in the positions which they 
would occupy for a cut-off at one-third stroke, the full 
line links being in position for the rearward stroke of 
the piston, and the dotted line links being in position 
for the forward stroke. The movement of the crank 






ERROR DUE TO ECCENTRIC ROD PINS. 



167 




American Machinist 



Fig. 98. 

is supposed to be by a Scotch yoke, so that no con- 
necting rod errors are introduced. It will be seen at 
once that the setting of the eccentric rod pins back of 



1 68 SLIDE VALVE GEARS. 

the link arc makes the lines joining the extremities of 
the arc and the centres of the eccentric crooked, 
whereas with this pin located on the arc, this line is of 
course straight ; consequently the effect of placing 
these pins back of the arc is for the positions shown, 
to draw the link having the offset pins nearer the shaft 
than the link which has the pins on the link arc. The 
action is that of a knuckle joint, any bending of which 
must draw the link toward the shaft. The rock shaft 
reverses this action on the valve, so that this drawing 
of the link toward the shaft pushes the valve away 
from the shaft. Pushing the valve away from the 
shaft quickens the cut-off for the front port or rearward 
stroke, and delays it for the rear port or forward stroke ; 
that is, the effect of the offset pin is to make the cut- 
off too early in the rearward stroke and too late in the 
forward. 

This effect will be seen to be the direct opposite of 
those produced by the connecting and eccentric rods, 
and it obviously calls for an adjustment of the saddle 
stud in the opposite direction, as shown in Fig. 99, 
which shows the position of the saddle stud necessary 
to equalize the cut-off at one-third stroke with the 
Scotch yoke connection, the stud being on the con- 
cave side of the link, where it is in all cases located in 
actual engines. 

Summing up, Fig. 93 shows the offset of the stud 
necessary to compensate the error of the connecting 
rod alone ; Fig. 96 shows the offset necessary for the 
eccentric rod error alone, while Fig. 99 shows the off- 
set to compensate the effect of the location of the 
eccentric rod pins. The diagrams have been carefully 



ERROR DUE TO ECCENTRIC ROD PINS. 



l6g 



drawn to scale and the amounts of the offsets shows 
the relative importance of the three sources of error. 







American Machinist 

I 

Fig. 99. 



170 



SLIDE VALVE GEARS. 




Fig. 100. 



THE FINAL OFFSET. 



It is obvious that the final offset of the stud is the 
resultant of all three. The offset of the eccentric rod 






THE FINAL OFFSET. \J\ 

pins varies within narrow limits only, but the length 
of the eccentric rod varies within wide limits. It is 
obvious that since the error of short rods alone would 
place the stud farther outside the link arc than long 
ones, they subtract more from the offset of the stud 
due to the eccentric rod pins than long ones, the re- 
sult being that the final offset is less with short rods 
than with long ones ; and this is found to be the case, 
the offset in actual engines ranging between about five- 
eighths of an inch and one and a quarter inches, de- 
pending on the length of the eccentric-rods. The 
connecting rod also varies in length, but its influence 
is so small that the variation in its length between 
usual limits has but little effect on the final result. 
To illustrate this, Fig. ioo has been constructed, in 
which the connecting rod has been shortened by trial 
until the offset of the saddle stud disappeared, placing 
that stud over the link arc. With the other propor- 
tions unchanged, it was found necessary to shorten 
the connecting rod to a remaining length of three feet 
before this result was accomplished. 

In the diagrams in which the saddle stud is located 
the following proportions have been used : 

Stroke of piston, 24 inches. 

Length of connecting rod, 91 inches. 

Radius of link arc, 69 inches. 

Length of link between pin centres, 12 inches. 

Offset of eccentric rod pins, 3 inches. 

Travel of valve, ^\ inches. 

Lap, \ inch. 



172 SLIDE VALVE GEARS, 



THE ADJUSTMENT OF THE SADDLE STUD. 

The adjustment of the residual error is accomplished 
by so suspending the link that it rises and falls in the 
course of its movement, in consequence of which the 
point acting upon the link block at cut-off in the rear- 
ward stroke is different from that acting in the forward 
stroke. Points of the link near the centre give earlier 
cut-offs than those removed from the centre, and it is 
obvious that by so suspending the link that the point 
acting upon the link block is different for the two 
strokes, the two points of cut-off may be altered as 
desired. 

There are two methods by which this movement of 
the link can be accomplished. One, which is in uni- 
versal use, consists of placing the saddle stud back of 
the link arc, the effect being obviously to cause the 
arc to rise and fall during its oscillation. The second 
method consists of so locating the tumbling shaft that 
the link hanger does not oscillate equally each side of 
the vertical line, but more on one side of this line than 
the other, the effect of which is obviously to cause the 
entire link to bodily rise and fall during its movement. 
These two methods are usually described in detail in 
discussions of this kind, with diagrams showing how 
the location of the suspension stud and of the tum- 
bling shaft may be laid down upon the drawing board. 
In point of fact, however, they are not so located, and, 
moreover, the second method is seldom employed, as 
the choice of location of the reverse shaft box is usu- 
ally quite restricted, and the designer is not at liberty 



ADJUSTMENT OF SADDLE STUD, 



173 



to place it in the position which this consideration 
would indicate. The location of the saddle stud is 




American Machinist 



Fig. 101. 



determined by triai upon the engine itself, an adjusta- 
ble stud being provided, shown in Fig. 10 1, which is 



174 SLIDE VALVE GEARS. 

bolted to the link, when, by trial adjustments, the 
proper position is found. The link is then removed 
from the engine and with the adjustable stud is taken 
to the link shop, where the permanent stud is made in 
accordance with it. In the case of a number of dupli- 
cate engines gotten out at the same time, the adjusta- 
ble stud is applied to the first one only and the follow- 
ing engines of that lot have their permanent studs 
made in duplicate. 

THE PROPORTIONS OF THE LINK MOTION. 

Of design, in the sense in which that word is under- 
stood in connection with most other lines of machine 
work, there is very little connected with link motion. 
As the outgrowth of long experience, the leading di- 
mensions of the gear are largely stereotyped in any 
given locomotive works, and between the work of dif- 
ferent builders the differences are small. The follow- 
ing table of dimensions, taken from representative 
engines of various sizes as built by the Schenectady 
Locomotive Works, gives some of the leading dimen- 
sions. As contrasted with stationary practice, the lap 
for any given travel of valve is much smaller, because 
the cut-off in the full gear is later than would be em- 
ployed in any stationary engine having a fixed cut-off, 
and because an increase in the lap would reduce the 
port opening at short cut-off. The exhaust edge of the 
valve varies in design between about 1-32 inch lap and 
-|-inch clearance, the clearance being usually given to 
passenger engines. 



REPRESENTATIVE LINK MOTIONS. 



175 





1 


1 








O 








•a 


g 










c 

Ph 


bo 


cu 
he 

03 






CU 

3 

C 


ri C 


CU c 
hxjO 

03 '3 




cu 


J 




9) 


CO 

Ph 

a 

o3 
<U 

*0 

CO 


a 

cu 


CO 

u 

CD 




s 




cue/) 


Size and Class of 
Engine. 


> 

> 



> 


c 
<u 


W 

"o 


a 


CU • 

n « 

•* h 


. 

o3< 

co C 

o3 
o3 tn 


> 
Q 



cu 
1u 


X 
Pi' 


cu 

a 

CU 

CU 


+J CU 

<+H CO 

O tn 


Ph$£ 

03 3.S 
03 ^W 




o3 
u 

H 



^3 






J3 


.2 


WjPL, 
< 


o3 


a 

C/) 


CU 

a 

CO 


.^Ph 








H 




hi 
c 

■J 


6 
S 


hfl 

o3 

CO 
CO 

Pi 


s 




C 
O 

CO 


if 

> 


cu'3 

CO M 
Ph^ 




1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


II 


13x18 N. G. 8 Wheel Frt. 
























& Pass 


5 


4& 


% 


10M 


12x1^8 


.099 


49 


30 


620 


105 


•95 


14x18 Forney Suburban . . 


5 


4* 


8 


10K 


12X1^4 


.088 


43 


25 


590 


112 


.89 


15 x 22 -8-Wheel|^t s;:: 


5M 


5X 


H 


12 


14X1%: 


.099 


63 


30 


585 


99 


1. 01 


5^ 


5K 


% 


12 


HXlK 


.099 


63 


35 


680 


115 


.87 


16x24-8- Wheel | g£ g ; ; ; 


5K 


S% 


% 


12 


•I4XlJ< 


.087 


63 


30 


640 


123 


.81 


5M 


sA 


% 


12 


14X1^ 


.087 


68 


35 


690 


132 


.76 


i 7 x 24 -8-Wheel j gj^; ; ■ 


5% 

5K 


sA 




12 
12 


l6Xl% 
l6Xl% 


.088 

.088 


63 
68 


30 
35 


640 
690 


121 

131 


.83 
.76 


18x24— 8-Wheel Pass. ! '. \ 


5K 


sA 


% 


12 


16X1% 


.079 


67 


35 


705 


149 


*7 


i 9 x2 4 -io-Wheel |£f ss ; 


r5^ 


sA 

5A 


A 
% 


12 
12 


l8Xl*< 

18x1% 


.08 
.08 


63 
68 


30 
40 


640 

790 


134 
165 


•75 
.61 


19x24 — 8-Wheel Pass. . . . 


6 


SA 


*x 


13 


20Xl^i 


.097 


75 


45 


805 


I38 


.72 


20x24 — 8-Wheel Pass. . . . 


6 


sH 


i/ 8 


13 


20X1^ 


.088 


73 


45 


830 


157 


.64 


2ox 24 -io-Wheel |£f ss ; 


5^ 


sA 


H 


12 


l8XlJ< 


.072 


63 


30 


640 


I48 


.68 


sM 


sA 


7 A 


12 


l8XlX 


.072 


68 


40 


790 


183 


•55 


2ox 2 6-io-Wheel j p^ s ] 


6 
6 


6 

sA 


Vs 


13 
13 


18X1^ 
l8Xl^ 


.079 
.079 


57 
68 


25 
40 


635 

855 


134 
180 


•75 
•55 


20x26 — C n s 1 i d a t ion 
























slow Frt 


s% 


sA 


A 


12 


18XI 3/^ 


.079 


50 


20 


585 


123 


.81 


21x26 — C n s 1 i d a t ion 
























slow Frt 


sA 


sA\ 


A 


12 


18X1^ 


.072 


50 


20 


585 


135 


•74 



PROPORTIONS OF REPRESENTATIVE LINK MOTIONS. 



From the above table it will be seen that, with a 
valve travel of 5 or 5^ inches, the lap in freight loco- 
motives is uniformly J inch. In the case of the 20 x 
26 ten-wheeled freight engine, in which the travel is 6 
inches, the lap becomes 1 inch. In the case of pas- 
senger engines having a travel of 5 inches, the lap is f 



I7 6 SLIDE VALVE GEARS. 

inch, and in case of those having a travel of 5| inches, 
| inch. With passenger engines having a lap of 6 
inches, the lap becomes \\ and I \ inches. The differ- 
ence between the travel of the valve and the throw* of 
the eccentric usually grows out of the location of the 
point at which it is convenient to locate the rock shaft ; 
this point being ordinarily such as to make the lower 
end of the rocker arm somewhat shorter than the upper 
end. To provide for lost motion and wear due to the 
numerous joints, it is customary to give the eccentric 
such a throw as to give a calculated travel of valve \ 
inch greater than is desired, and if the length of the 
rocker arms were given in this table and the valve 
travel calculated, it would appear as \ inch greater 
than the figures of the table. The actual travel is, 
however, confined to the desired amount by the limi- 
tation placed upon the throw of the reverse lever. 
With the exception of the 20 x 26 ten-wheeled freight 
engine, the length of the link between pin centres 
ranges between 2.2 and 2.3 times the throw of the 
eccentric. It will be seen that the velocity of the 
steam through the port is quite uniformly less in the 
case of freight engines than in passenger engines, ow- 
ing to the fact that it is customary to use the same 
sized ports for a given cylinder, regardless of its duty, 
and the piston speed being lower in the freight engines, 
the velocity of the steam is less. There is sound rea- 
son in this, growing out of the fact that the terminal 
pressure in freight engines is higher than in passenger 

* "Throw " is here used in the locomotive sense of double the 
eccentricity. 



THE AREA OF THE PORTS. \JJ 

engines. The usual method for calculating the velocity 
of the steam is, in fact, defective, as it takes no ac- 
count of the increased amount of steam contained in 
the cylinder at high terminal pressure over that con- 
tained at low. In a general way this is met by the 
practice described. 

THE AREA OF THE PORTS. 

One of the purposes of the table on page 175 is to 
make some comparisons between the port areas of 
stationary and locomotive engines. These will be 
found in the sixth, tenth and eleventh columns, and 
to the stationary engine designer will be the most 
interesting part of the table. Owing to the great vari- 
ations in the speed of the same locomotive under dif- 
ferent conditions, no exact comparison of this kind is 
possible. The speeds desired for this purpose are the 
average speeds, but who shall say what these are? 
Under these circumstances the only basis of compari- 
son seems to be the schedule or time-card speed, and 
the speeds given in miles per hour are the time-card 
speeds for which the engines are considered suitable, 
and it is from these that the piston speeds and steam 
velocities have been calculated. Of course the aver- 
age running speeds must be greater than the time-card 
speeds, and the true velocities of the steam corre- 
spondingly greater, and while the port areas of the 
table seem small, they would seem smaller still could 
they be calculated from the true average running 
speed. As will be seen by the tenth column of the 
table, the velocity of the steam in locomotive ports 



178 SLIDE VALVE GEARS. 

is, for all sizes, decidedly greater than the 100 feet 
per second which forms the basis of the usual rules for 
stationary engines. The eleventh column of the table 
compares the actual passages employed in locomotives 
with those which the stationary engineer would give, 
and shows them, of course, to be much smaller, even 
on the basis of time-card speed. Could the calcula- 
tions be made on the mean running speed, there is no 
doubt that the ports of most of the large passenger 
engines would be found to have less than one-half the 
cross-section commonly provided in stationary engines. 
It should be explained that in locomotive work it is a 
common practice to make that portion of the passage 
which runs paralled with the cylinder \ inch wider than 
that leading from the valve-seat, as the inaccessibility 
of the first portion makes it impossible to clean it out 
or correct errors in the casting, while the second por- 
tion may be easily reached for that purpose. The 
portion of the passage, for which figures are given in 
the table, is the larger portion parallel with the cyl- 
inder. 

PORT OPENING AND AREA OF NOZZLE. 

If, however, these ports seem small, the openings 
of them to steam are still more so. Thus in the case 
of the 19 x 24 eight-wheeled passenger engine, the 
opening to steam at 8-inch cut-off is only 7-16 inch, 
and in the case of the 20 x 24 eight-wheeled passen- 
ger engine, the opening is but f inch, these openings 
being in area but 39 per cent, and 3 1 per cent, of what 
would be required by the customary stationary engine 



BLAST NOZZLE AREAS. 



179 



rule, which requires the opening for steam to be three- 
fourths of the port given by the rule cited above. 

BLAST NOZZLE AREAS, COMPARED WITH PISTON AND 
PORT AREAS. 

Small as these ports seem, to a stationary-engine 
designer, it is, however, an open question if they 
are not larger than necessary or advisable. The 
point where the steam meets with the greatest resist- 
ance in its escape from the cylinder is the blast nozzle. 
These nozzles were formerly made separate for each 
cylinder, the diameter of this pattern of nozzle for an 
18 x 24 eight-wheel passenger engine ranging between 
2 -J inches and 3^ inches. Taking the mean of these, 
3 inches, as the average, its area is but 2.8 per cent, 
of that of the piston, or but 35 per cent, of the area of 
the port. The port would naturally be made larger 
than the nozzle ; but it would certainly seem that 
there is no occasion for so great a difference as these 
figures show. At present locomotives are more usually 
made with a single nozzle, through which the steam 
from both cylinders escapes, the diameters of these 
nozzles being about as shown in the following table, in 
which also their areas are compared with the combined 
areas of the two pistons and of the two ports. Of 
course a given area of nozzle arranged in this way 
gives less resistance than the same area in two sepa- 
rate nozzles, as the puff at release alternates between 
the cylinders; but making all allowance for this, it 
will be seen that the resistance of the nozzle must be 
far in excess of that of the port. 



i8o 



SLIDE VALVE GEARS. 



Size and Class of Engine. 



i 8 x 24— 8-Wheel Pass. . 

19 x 24 — 8-Wheel Pass. . 

20 x 26 — 10-Wheel Frt. . 
20 x 26 — 10-Wheel Pass 
20 x 26 — Consol. Frt. . . . 







<U crt 


N 
O 




73 c 

N O 

li 








c 




c^^o 


**H <U 




c a 


C, N 




a <u 






<u ^ 








V 







S 

S 






4i 4 4f 


.031 


4* 5 


54 


.035 


4* 5 


sl 


.031 


5 5i 


54 


.034 


4* 5 


54 


.031 



0> N 



5- 

< OJ 

.4 

,36 

.4 

.44 

•4 



SMALLER PORTS ADVOCATED. 

In this connection, some remarks by Mr. Angus 
Sinclair, in "Locomotive Engineering " for April, 
1897, are of great interest. Mr. Sinclair made use of 
his opportunities to measure the ports of several Eng- 
lish locomotives, and found them to range between 10 
and 13 inches in length, the width being about 1^ 
inches, and Mr. Sinclair pertinently asks if the greatly 
increased clearance space due to the large ports of 
American locomotives is not at least partly responsible 
for the wastefulness of fuel with which they are com- 
monly credited. In this connection Mr. Quereau's 
indicator cards, given in Fig. 80, are instructive. 
These cards were taken from an engine having its 
valve set to give a greatly reduced lead, as compared 
with ordinary practice, the result being to show clearly 
the termination of the compression line. Cards taken 
from engines having the valves set with the usual 
amount of lead, show the compression line running 



SMALLER FOR TS AD VOCA TED. I 8 I 

into the lead line in such a manner as to give the im- 
pression that the compression is continuous up to or 
even beyond boiler pressure, and the large clearance 
spaces heretofore used have been considered necessary 
to provide room for this compression. Mr. Quereau's 
cards show that the compression does not reach any- 
where near boiler pressure, and that the clearance vol- 
ume is not needed for this purpose, and in view of this, 
of the above comparison of nozzle and port areas and 
of English practice with smaller ports, it is at least a 
subject of doubt if American ports are not too large 
for the best results. 

No adequate experiments have ever been made to 
settle this question. It, of course, involves some risk 
to equip an engine with cylinders having small ports, 
and such experiments as have been made have been 
with the usual size of ports reduced at the opening by 
a false valve seat. Inasmuch as the expected benefits 
of smaller ports would be due to the reduced clear- 
ance, which is not affected by the valve seat, it is clear 
that no conclusions can be drawn from such experi- 
ments regarding the real value of the change. The 
most that can be expected is to demonstrate that the 
smaller ports are not harmful. It would seem that 
any such change should be in the width, rather than 
the length, of the port. A change in the length 
affects both admission and exhaust, while a change in 
width affects the exhaust only. Injury and not im- i 
provement is to be anticipated from the reduction of 
admission area, which should obviously be avoided. 

Many years ago, Wilson Eddy, then master me- 
chanic of the Boston & Albany Railroad, made many 



1 82 SLIDE VALVE GEARS. 

engines with small ports, even down to a length of 8 
inches, and his conclusions were that the standard 
sizes of ports were too large. In this connection, it 
must be remembered that back pressure is a very dif- 
ferent factor in locomotives from what it is in station- 
ary engines. With the latter it is an unmixed evil, 
but with the former it is a necessity. With stationary 
engines the boiler and the engine are practically inde- 
pendent structures, but in locomotives they are inte- 
gral parts of the same machine, each reacting upon the 
other. The boiler not only supplies steam for the 
engine, but the engine, through its exhaust, supplies 
draft for the fire, and without the draft and the back 
pressure which produces it, the steam could not be 
made nor the engine operated. 

RESULTS FROM ACTUAL ENGINES. 

The adjustment of the saddle stud is, of course, 
made to equalize the cut-off at some one point of the 
stroke — usually at one-third stroke. To attempt to 
study the degree to which the various influences com- 
pensate one another at other points would lead us far 
afield, and the facts can be best seen by studying the 
results from actual engines. These are given in link 
charts Nos. I and 2, which are from eight-wheeled pas- 
senger engines and give a complete record of the right- 
hand side of two locomotives built by the Schenectady 
Locomotive Works. These charts are in no way ex- 
ceptional, but are representative of what is done every 
day. The first two columns give the lead in the vari- 
ous gears, the second two columns give the port open- 
ings, from which the great reduction of port opening 



RESULTS WITH ACTUAL ENGINES. 



I8 3 



in early gears will be seen. It should be mentioned 
to avoid misunderstanding, that the port opening given 
in the full gear means the distance by which the valve 
uncovers the outer edge of the port. In locomotive 
practice this exceeds the actual width of the port, this 
excess of travel being given in order to obtain more 
port opening in the early gears. It will be seen that 
the equality of the cut-offs obtained is excellent, there 
being no appreciable difference up to the half stroke 



Link Chart No. i. 

Schenectady Locomotive Works, 
Feb. 21, 1895. 
Built for St. Lawrence & Adirondack R. R. Engine 
No. 4437. Size of Cylinders, 18" x 24". Size of 
driving wheels, 67". 



Lead. 


Valve 


Opens. 


Cut 


Off. 


Remarks. 


Forward 


Rearward 


Forward 


Rearward 


Forward 


Rearward 


Offset |" 


Stroke. 


Stroke. 


Stroke 


Stroke. 


Stroke. 


Stroke. 


tV 


l " 


1. 1" 


if" 


2l" 


2I T V 


Slip 1". 


3 " 
3¥ 


3 " 
3T 


ift" 


ift 


20" 


20 J" 




1 " 


1 '' 


7 " 


7 " 

8 


18" 


ISA" 




3 " 


ft 


13" 


13" 


16" 


i6 T V 




7 " 
T2 , 


7 " 
TZ 


5 " 


5 " 


14" 


I4tV 




f ;;F . 


| ;; f. 


1 " 

7 " 


1 " 

7 '' 
TF 


12" 
10" 


12" 
10" 


Slip f ". 


9 " 
3T 


9 " 
z~Z 


1" s. 


3 " C 


8" 


8" 




9 " 


9 " 
"5T 


5 " 


5 " 
IT 


6" 


6" 





Passsenger service, four coupled wheels, 
of link, 69". Length of main rods, 98V. 
Travel, 5^", 



Radius of 
Lap, J 



"S~ 



1 84 



SLIDE VALVE GEARS. 



in chart No. I, while the largest difference in the 
entire range is only 5-16 inch, which is found in the 
full gear. In chart No. 2 the action is not quite so 
good in the early gears, but is still better in the late 
ones. This surprisingly good adjustment shows that 
nothing of consequence is sacrificed by neglecting the 
location of the reverse shaft as has already been 
described. 



Link Chart No. 2. 

Schenectady Locomotive Works, 
June 1, 1896. 
Built for the New York, New Haven & Hartford 
R. R. Engine No. 4442. Size of cylinders, 

20" x 24". Size of driving wheels, 73". 



Lead. 


Valve Opens. 


Cut Off. 


Remarks. 


Forward 


Rearward 


Forward 


Rearward 


Forward 


Rearward 


" 


Stroke. 


Stroke. 


Stroke 


Stroke. 


Stroke. 


Stroke. 




1 " 
T6" , 


1 " 
T6 , 


T 15" 


T 15" 
I T6 


20iV' 


20 i" 


Slip if. 


3 " C 


3 " c 

3^ ^ 


lit" 


lit" 


20" 


2o T y 




1 " 
8 


1 " 
8 


li" 


li" 


18" 


18 i" 




5 " 
3T 


5 " 
82 


1 5" 
"16 


15" 
T6 


16" 


i 4 * 




d 3 " C 

TB", ^- 


3 " C 
T6 3 - 


11" 
T6 


1 1" 
1 6 


14" 




A F- 


A" F- 


9 " 
T6 


9 " 
TS 


12" 


1 iir 


slip H"- 


ft' s. 


7 " C 


15'' S 
32 °* 


15" C 
3¥ 3 ' 


10" 


9* 




7 " 


7 " 
3 2 , 


1" 


3 " 

"8" 


8" 


«15" 




7 " "F 


7 " T? 
•3¥ r « 


A" 


5 " 
T6 


6" 





Passenger service, four coupled wheels, 
link, 6o£". Length of main rods, 94". 

Travel, 6". 



Radius of 
Lap, 



T l" 



PRA C TICE IN VA L VE SE T TING. 1 8 5 



RECENT PRACTICE IN VALVE SETTING. 

It was formerly the universal, as it is still the usual, 
practice when setting locomotive valves, to give them 
a small (about 1-16 inch) lead in the full gear, and 
then allow them to take such leads for shorter cut-offs 
as the proportion of the parts, especially the length 
of the eccentric rods, should determine. Of late a 
more rational method has been practised to some ex- 
tent, which is undoubtedly growing and destined to 
grow still more. This method consists in adjusting 
the lead for the running cut-off, instead of the full 
gear, the leads for the other gears being largely deter- 
mined by the mechanism. This involves a negative 
lead or blind port in one or both full gears ; but as 
might have been expected, this is found to have no 
deleterious effect on the running qualities in the full 
gear, owing to that gear being used only at starting, 
when the speed is low, and with the large port open- 
ing of the full gear no lead is required to properly fill 
the cylinder with steam. In point of fact, negative 
lead in the full gear is claimed by many to be an ad- 
vantage and to give an appreciable increase to the 
power of the engine when running in the full gear, 
due to the fact that positive lead offers resistance to 
the motion of the piston. The effect of the reduced 
lead in the running gear is to cause the engine to ride 
easier, to reduce the frequency of hot bearings, and, 
by reducing the strain to lessen repairs. A slight gain 
in fuel economy is also claimed by some, due to the 
reduction of hurtful resistance to the motion of the 



1 86 



SLIDE VALVE GEARS, 



piston and to a slight prolongation of expansion before 
release. 

A leader in this movement is Mr. C. H. Quereau, 
of the Chicago & Missouri River Railroad, in Nebraska, 
who has done a good deal of experimenting on the 
subject and has presented his conclusions in a paper 
before the Western Railway Club. Mr. Quereau gives 
gives several indicator cards from the same engine with 
various settings of the lead, of which Figs, 102, 103, 



aoo" 




Fig. 102. 

Lead at Cut-off ±i". 
Speed 55 M. P. H. 

and 104, are presented as examples. The effect of 
the change upon the steam distribution is apparent at 
once. The fact that the compression does not rise to 
boiler pressure, which has been already referred to, will 
be seen, and from which deductions regarding the size 
of ports has been drawn. 

This practice has been adopted by many progressive 
superintendents of motive power and railroad master 
mechanics. It is endorsed by the mechanical officers 



PRACTICE IN VALVE SETTING. 



I8 7 



of the New York, New Haven & Hartford; Maine 
Central; Chicago, Burlington & Quincy; Chicago, 
Burlington & Northern ; Chicago & Northwestern ; 




American Machinist 



Fig. 103. 

Lead at Cut-off A". 







American Machinist 



Fig. 104. 

Lead at Cut-off ^". 

Speed 55 M. P. H. 

Illinois Central ; Boston & Maine ; Lake Shore & 
Michigan Southern and other leading roads. 

The reduction of the lead in the running gear 



I 88 SLIDE VALVE GEARS. 

may be brought about by setting back the forward 
eccentric or the backing eccentric, or both, and in the 
latter case in equal or unequal amounts. Railroad 
mechanics who agree on the main point of a reduced 
running-gear lead, differ in the method used to accom- 
plish it. Following is the practice of several roads in 
this respect : 

The New York, New Haven & Hartford gives to 
fast passenger engines 1-16-inch positive lead in full 
gear forward, and 1-4-inch negative lead in the full gear 
back, resulting in 1-4-inch positive in the running gear. 

The Maine Central sets the valve line and line for 
the full gear forward, and gives 1-4-inch negative lead 
in the full gear back on passenger engines. 

The Illinois Central gives to passenger engines 1-32- 
inch positive lead in the full gear forward and then 
adjusts the backing eccentric to give about 3-16-inch 
lead in the running cut-off. 

The Lake Shore and Michigan Southern gives to 
passenger engines 1-16-inch negative lead in the full 
gear forward and 9-64-inch negative lead in the full 
gear back, resulting in about 5-16-inch lead for the 
running cut-off. 

The Chicago Great Western sets the valves of pas- 
senger engines line and line in both forward and back 
full gears, resulting in from 3-16-inch to 9-32-inch lead 
at 6-inch cut-off, and on mogul freight engines gives 
3-64-inch negative lead in both full gears, resulting in 
1-4-inch lead at 6-inch cut-off. 

The Chicago & Northwestern recently specified for 
some 19 x 24 passenger engines 3-16-inch negative 
lead in the full gear forward and 1-4-inch positive lead 






°0 


to 


s 


Q> 


^ 


*^ 


« 




^ 




Su 


-^ 




u; 


s 



PRACTICE IJV VALVE SETTING. 1 89 

at 6-inch cut-off, obtained by adjusting the backing 
eccentrics. These engines had Allen valves. 

The diversity of practice is apparent, but doubtless 
many of the apparent discrepancies would dissappear 
if the full details of the motions were known. The 
effect of the length of the eccentric rods is so marked 
on the midgear leads that it has doubtless had an 
influence on the methods followed in different cases, 
even when substantially the same running gear lead 
has been arrived at. 

The analysis of the action of the various settings of 
the eccentrics can best be made by means of the Bil- 
gram diagram. Referring to Fig. 48, it will be seen 
that in order to determine the properties of the gear it 
is only necessary to know the location of the line QQ°, 
and on this draw the lap circle for various points of 
cut-off. The point Q may be located directly from the 
lap and the full gear lead, and the point Q° from the 
lap and midgear lead. The full gear lead is usually 
assumed at the beginning, but the midgear lead varies 
with the length of the eccentric rods and must be 
found. This is done in the manner shown in Fig. 105. 
The diameter of the dotted circle is equal to the full 
gear travel of the valve — 6 inches — and points aba' b[ 
are laid down at a horizontal distance from the vertical 
centre line equal to the lap \\ inches, From these 
points the full gear lead 1- 16-inch is laid down, giving 
points c d c d' y which the eccentrics occupy when the 
crank is on the centres. From these points the full 
and dotted positions of the link are easily found, with 
the resulting midgear travel e f, which by measuring is 
found to be 3-f inehes. Dividing this in half and sub- 



190 



SLIDE VALVE GEARS. 



trading the lap i or o n gives the midgear lead if 
or e n> which is equal to *$ — ■ i-J- = T V inch. One 




American Machinist 



Fig. 106. 



ab — lap. 

b c — r s — full-gear forward lead — positive. 
b' c' = full gear backward lead — positive. 
de = I n = mid-gear lead. 



caution should be given here. When the eccentric 
throw and valve travel differ, it is most convenient to 
use the valve travel as the diameter of the circle, but 



PRACTICE IN VALVE SETTING. 191 

when that is done the eccentric rod lengths and the 
link dimensions should be enlarged from the actual 
in the proportion of the valve travel to the eccentric 
throw. 

Having the midgear lead determined, the Bilgram 
diagram, Fig. 106, can be constructed thus: draw the 
inner dotted circle equal in diameter to the full stroke 
valve travel, and lay down a b equal to the lap, make 
b c equal to the full gear lead, and d e equal to the 
midgear lead, as found in Fig. 105. Now, a circle 
struck through e f g will give the path on which a sin- 
gle shifting eccentric must travel to produce a valve 
movement equivalent to that given by the link of Fig. 
105. Laying off Ji f equal to h f, and e equal to 
e, the circular arc e f is easily drawn, on which the 
centre of the lap circle for all points of cut-off must lie. 
Drawing the outer dotted circle to represent the path 
of the crank pin to scale, and selecting, say, the cut-off 
at one-third stroke for study, the point i is laid down 
such that ij equals one-third of the stroke, and by the 
perpendicular ik the crank line O k for one-third stroke 
is located. This is extended upward,* and the lap 
circle i 5 drawn tangent to it with its centre on the line 
e f. We now have for the one-third cut-off a lead 
equal to / n, a port opening equal to o, a travel 
equal to twice Op, an exhaust opening and closure 
(assuming no inside lap) at crank position q. Simi- 

* Because the American locomotive valve gear always has a 
rocker. It will be recalled that the previous Bilgram diagrams 
were for gears having no rocker, in which case the lap circle is tan- 
gent to the crank centre line and not to its extension. 



ig2 SLIDE VALVE GEARS. 

larly we have for the full gear a lead r s equal to b c> a 
port opening /, a travel equal to twice f ', and an 
exhaust opening and closure at crank position n. 

The effect of making the full gear leads negative is 
seen in Figs. 107 and 108. Proceeding in Fig. 107 as 
before in Fig. 105, and laying down the dotted circle 
equal in diameter to the valve travel, we lay down 
a, b, d, b' , to right and left of the centre line by a dis- 
tance equal to the lap — as before 1^ inch. The full 
gear leads being negative, the points c, d, c\ d will 
come inside of a, b, a, b\ instead of outside, as in Fig. 
105. Assuming a full forward gear negative lead 
of \ inch, c and c are laid down with a horizontal dis- 
tance of \ inch inside of a and d ', and similarly assum- 
ing a full backing gear negative lead of \ inch, d and 
d are laid down with a horizontal distance of \ inch 
inside of b and b f . From these points c, d, c' d the 
dotted link positions for the two crank centres are 
located, showing the midgear travel to be e f, which 
by measurement is found to be 2f inches. Dividing 
this by two, as before, and subtracting the lap o i or 
7i, the midgear lead i f or e n is found to equal ^ — 
\\ — \\r\<3\. Repeating the construction of Fig. 106 
in 108, remembering that the full gear leads b c and 
b r c r are negative, gives the arc f e g for the line of 
travel for the equivalent shifting eccentric, from which 
the arc e r f is easily located, as was done in Fig. 106. 
Drawing the crank line k for one-third stroke as 
before, and the lap circle tangent to it, gives at once 
the lead, port openrng, travel, release, and compres- 
sion for one-third cut-off in the modified gear. The 
action in the full gear is also shown, the lead r s being 



if' 



"1 






^ 




On 


rv. 


s 


Q> 


^ 


^. 


sf 




■*1 






■ S> 


Vj 


c 


S 




£ 



PRACTICE IN VALVE SETTING. 



193 



shown to be negative by the lap circle going below 
the horizontal centre line. Figs. 106 and 108 are 
both repeated in Fig. 109, the former in full and the 




American Machinist* 



Fig. 108. 

a b — lap. 

b c = r s = full-gear forward lead— negative. 
b' c' = full-gear backward lead— negative. 
d e = / n = mid-gear lead. 

latter in dotted lines, in order that the effects of the 
modified setting may be more easily compared. It 
will be seen that for the one-third cut-off, the lead and 



194 



SLIDE VALVE GEARS, 



port opening are both reduced, while the release and 
compression are both 'made later. Similar changes 
are also seen in the full gear and additional lap cir- 




Ameriean Machinist 



Fig. 109. 



cles for other points of cut-off would show similar 
changes. 

Link charts Nos. 3 and 4 give the records of two 
locomotives having the modified valve setting. 



RESULTS WITH ACTUAL ENGINES. 



195 



Link Chart No. 3. 

Schenectady Locomotive Works, 

, 1897. 

Built for the Northern Pacific Ry. Engine No. 
4542. Size of cylinders 20" x 26". Size of driving 
wheels, 69". 



Lead. 


Valve Opens. 


Cut Off. 


Remarks. 


Forward 


Rearward 


Forward 


Rearward 


Forward 


Rearward 




Stroke. 


Stroke. 


Stroke 


Stroke. 


Stroke. 


Stroke. 




1 "blind 


i" blind 


if" 


i|" 


22A" 


22 f " 


Slip if". 


■3V blind 


3V blind 


ItV 


ItV 


2l" 


2l" 




■3V' lead 


3V lead 


ItV 


ItV 


19" 


19" 




3 " 

32 


3 " 

32 


23" 
¥2 


2 3" 


16" 


16" 




1 " 

8 


F 


1 " 
2 


1 " 
2 


13" 


L J 8 




A' 


9 " 
6¥ 


3 " 

8 , 


3 " 
' 8 


10" 


10" 


Slip if. 


3 2 °' 


5 " C 
"32" 3 * 


16 


tV 


8" 


8" 




5 " 
32 


5 " 

3 2 


1 " 


1 " 
¥ 


6" 


6" 




5 " f 


32 r • 


7 " 
3~2 


7 " 

■T2 - 


4" 


4tV" 





Passenger service, six coupled wheels. 
Length. of main rods, 126I". 
Radius of Link, 40". 



Lap, i-J-". 
Travel, 6". 
Allen valve. 



196 



SLIDE VALVE GEARS. 



Link Chart, No. 4. 

Schenectady Locomotive Works, 
Sept. 18, 1895. 
Built for the Chicago and Northwestern R. R. En- 
gine No. 4337. Size of cylinders, 19" x 24". Size 
driving wheels, 75". 



Lead. 


Valve Opens. 


Cut Off. 


Remarks. 


Forward 


Rearward 


Forward 


Rearward 


Forward 


Rearward 


Offsetff" 


Stroke. 


Stroke. 


Stroke 


Stroke. 


Stroke. 


Stroke. 


^" blind 


T 3 g-'' blind 


if" 


it" 


20 T V 


20 K 


Slip |". 


•gV blind 


A" blind 


i*' 


1*" 


20" 


20 1" 




■3V blind 


A" blind 


ii" 


ii" 


18" 


18 j" 




line&line 


line&line 


i" 


I 


16" 


16A" 

14 




A" lead 


A" lead 


f'S. 


1" 


14" 




5 " 


5 " 


A" 


A 


12" 


12" 


Slip f". 


3 " 


3 " 


1 ' 
2 


1 '* 


10" 


10" 




-V' 
3^ 


■X" 


7 ' 


7 " 
T6 


8" 


8" 




1 " 


1 " 


3 " 


3 " 

8 


6" 


6A" 





Passenger service, four coupled wheels. 
Length of main rods, 91^". 
Radius of Link, 59^'. 



Lap,!*". 

Travel, 6". 

Allen valve. 



INDEX. 



Adjustable saddle stud 173 

Adjustment of saddle stud 172 

Admission 13, 19, 21, 23 

Advance angle 18 

Allen valve, the 69 

Angle, exhaust lap 25^ 

lead 2$a 

" lap 15 

" lead o 23 

Angular advance 18 

11 vibration of connecting rod, error due to 45, 158 

11 eccentric rods, error due to 49, 85, 162 

Area of blast nozzle in locomotives 178 

Areas of blast nozzle, piston and ports compared 179 

11 " the ports and pipes 42 

Area of ports in locomotives 177 

Armington & Sims valve, the . 73 

Armstrong valve, the 72 

Backward rotation 11, 26 

Bilgram diagram applied to link motion 151, 189 

the 28 

" valve gear, the 122 

Buckeye valve gear, the. 116 

Cavity, influence of the exhaust 39 

11 width of the exhaust 38 

Centres, locating the engine on the 59 

Clearance, inside 4 

Compression 15, 21, 23 

advantages of, in locomotives 134 

Connecting rod a corrective factor 157 

" error due to angular vibration of 45, 158 

11 irregularities due to the 5 

" " of infinite length 47 

197 



198 INDEX. 

Crooked eccentric rods, effect of spring in 137 

Cross-head, the slotted 5 

Cut-off 13, 21, 23 

" and lead equalized 95 

* * equalized 54 

" the slide valve at short 67 

Cylinder problem of locomotive differs from that of stationary 

engine 135 

Defects of the primitive engine 13 

Diagram, the Bilgram 28 

" " applied to link motion 151,189 

Defense of link motion 134 

Dimensions of link motion, table of 175 

Eccentric, link motion compared with shifting 138 

position of, for either direction of rotation 27 

rods, effect of spring in crooked. 137 

" " error due to angular vibration of 49, 85, 162 

" " irregularities due to the 5 

" " long and short 147 

" " open and crossed 149 

the 4 

" " shifting 78 

" " swinging 80 

" throw of the 4 

" " " in locomotive sense 176 

Eddy, experiments of Wilson, on locomotive ports 181 

Engine, the primitive 7 

defects of 13 

Error due to angular vibration of connecting rod 45, 158 

" " " " " " eccentric rods 49,85,162 

" " *' location of eccentric rod pins back of link arc 166 

Errors of the link motion 157 

Equalization of link motion 1 54 

Equalized cut-off 54 

* * exhaust 50, 5 7 

lead 89 

" and cut-off 95 

Examples, illustrative 24, 35 

Exhaust cavity, influence of the , 39 



INDEX. 199 

Exhaust cavity, width of the 38 

" equalized 5°, 57 

lap 4, 25 

" " angle 25a 

1 ' negative i^d 

lead 31 

11 " angle 25a 

11 port opening 25^/, 31 

Experiments of Wilson Eddy on locomotive ports 181 

Gear, the Bilgram valve 129 

" " Buckeye " 11 

" " Gonzenbach valve 102 

11 " Meyer " 109 

11 " Straight Line " 54, 89, 120 

Giddings valve, the 74 

Gonzenbach valve gear, the 102 

Gridiron valve, the 103, 105 



Ide valve, the 74 

Influence of the exhaust cavity 39 

Illustrative examples 24, 35 

Lap 3, 15 

" angle 15 

V exhaust 25^ 

11 circle 31 

" effects of 18, 35 

1 ' how measured 4 

11 inside or exhaust] 4, 25 

11 negative 4, 26 

1 ' exhaust 25^/ 

11 outside or steam 3, 15 

11 positive and negative, how shown 31 

Lead 13,21 

and cut-off equalized 95 

angle 23 

il exhaust 25a 

equal and constant denned 77 

decreasing in early cut-off 82, 93, 122 



200 INDEX. 

Lead increasing in early cut-off 81 

4 ' equalized 89 

1 ' exhaust 31 

4 ' negative 93 

44 shifting link gives variable 143 

44 stationary link gives constant 142 

Limitations of the plain slide valve 40 

11 how overcome 67 

Link, action of, analyzed 153 

4 * correct radius of 147 

" motion and shifting eccentric compared 138 

" applicability of, to locomotive conditions 133 

" defense of 134 

" equalization of 154 

" 44 errors of the 157 

* * * ' proportions of 1 74 

44 the stationary, and shifting, compared 137 

44 table of dimensions of 175 

44 slip of the 156 

4 4 suspension of the 155 

44 the shifting, gives variable lead 143 

44 44 stationary gives constant lead 142 

Locomotives, distribution of steam in actual 182, 194 

recent practice in valve setting on 185, 194 

Meyer valve gear, the 109 

Negative exhaust lap 25^ 

lead 93 

Nozzle, area of blast, in locomotives 178 

44 piston, and port areas compared 179 

Offset of saddle stud 155, 157 

44 44 4< " final 170 

Opening, exhaust port 25</, 31 

port 18, 31 

44 44 definition of 42 

" of ports in locomotives 178 

" varying width of port 37 

width of port to steam 43 

Over-travel of the valve 42, 77 



INDEX. 20 1 

Pins back of link arc, error due to location of eccentric rod. . . . 166 

Pipes and ports, areas of the 42 

44 44 44 velocity of steam through the 43 

Piston nozzle and port areas compared 179 

Piston, speed of, in the two strokes 47 

Port opening 18,31 

44 denned 42 

44 exhaust 25^, 31 

44 in locomotives 178 

44 varying width of 37 

4 4 width of, to steam 43 

Port, piston, and nozzle areas compared 179 

Ports, area of, in locomotives 177 

44 length and breadth of 44 

44 multiple 68, 69, 72 

44 for the exhaust 70 

44 of English locomotives 180 

44 44 locomotives, experiments of Wilson Eddy on 181 

44 smaller ones advocated in locomotives 180 

Practice in valve setting on_locomotives, recent 185, 194 

Proportions of link motion 174 

Primitive engine, the 7 

defects of the 13 

Radius of link, correct 147 

Release 13, 21, 23 

4 4 proper location of the 102 

Reverse rotation 11, 26 

Rice valve, the 72 

Rock shaft 7, 27, 56 

Rod, error due to angular vibration of the connecting 45, 158 

44 44 eccentric 49, 85, 162 

4 4 connecting, of infinite length . 47 

44 the connecting, a corrective factor 157 

Rods, effect of spring in crooked eccentric 137 

44 long and short eccentric 147 

44 open and crossed eccentric 149 

Rotation, reverse 11, 26 

position of eccentric for either direction of 27 

Saddle stud, adjustable 173 

44 44 adjustment of 172 



202 INDEX. 

Saddle stud, final offset of 1 70 

" offset of 155, 157 

Scotch yoke, the 5 

Setting the slide valve 59 

Shaft, rock 7, 27, 56 

Shifting eccentric, the 78 

44 " and link motion compared 138 

4 ' link gives variable lead 143 

" motion compared with stationary 137 

Slide valve, laying out the 38 

44 limitations of the plain 40 

44 how overcome 67 

44 setting the 59 

44 the, at short cut-off 67 

" " the plain 3 

Slip of the link 156 

Spring in crooked eccentric rods, effect of 137 

Stationary and shifting link motions compared 137 

1 ' link gives constant lead 142 

Steam distribution of actual locomotives 182, 194 

11 velocity of, in locomotive ports 177 

'■ through pipes and passages 43 

Straight Line valve, the 69, 120 

44 " gear, the 54,89,120 

Stud, adjustable saddle 173 

44 adjustment of saddle 172 

4 ' final offset of saddle 1 70 

44 offset of saddle 155, 157 

Suspension of the link 155 

Swinging eccentric, the 80 

Throw of the eccentric 4 

44 44 " <4 in the locomotive sense 176 

Valve, laying out the slide 38 

44 limitations of the plain slide 40 

44 44 44 44 44 44 how overcome 67 

44 over-travel of the 42, 77 

44 setting, recent practice on locomotives 185,194 

44 44 the slide 59 

4 4 the Allen 69 






INDEX. 



203 



Valve the, Armington & Sims 73 

Armstrong 72 

Buckeye 116 

Giddings 74 

gridiron 103, 105 

Gonzenbach 102 

Ide 74 

Meyer 109 

Rice 72 

slide at short cut-off 67 

Straight Line 69, 120 

plain slide 3 

Woodbury 70 

44 velocity of the 39 

Valve gear, the Bilgram 122 

44 44 Buckeye . . 116 

11 " " Gonzenback 102 

" " 4 ' Meyer , . 109 

" " " Straight Line 54,89,120 

Velocity of steam through locomotive ports 177 

pipes and passages 43 

4 ' the valve 39 

Vibration of the connecting rod, angular 45, 158 

44 44 4 ' eccentric '* " 49,85,162 



Width of the exhaust cavity 38 

Woodbury valve, the 70 



Yoke, the Scotch. 



Catalogue of the Scientific Publications 

of D. Van Nostrand Company, 23 Murray 
Street and 27 Warren Street, New York. 



ADAMS, J. W. Sewers and Drains for Populous Dis- 
tricts. Embracing Rules and Formulas for the dimensions and con- 
struction of works of Sanitary Engineers. Second edition. 8vo, 
cloth $2.50 

ALEXANDER, J. H. Universal Dictionary of Weights 

and Measures, Ancient and Modern, reduced to the Standards of 
the United States of America. New edition, enlarged. 8vo, 
cloth $3.50 

ANDERSON, WILLIAM. On the Conversion of Heat 

into Work. A Practical Handbook on Heat-Engines. Illustrated. 
121110. cloth . . c $2.00 

ATKINSON, PHILIP. The Elements of Electric 

Lighting, including Electric Generation, Measurement, Storage, 
and Distribution. i2mo, cloth $* 5° 

AUCHINCLOSS, W. S. Link and Valve Motions 

Simplified. Illustrated with 37 woodcuts and 21 lithographic plates, 
together with a Travel Scale, and numerous useful tables. Tenth 
edition. 8vo, cloth „ $3.00 

AXON, W. E. A. The Mechanic's Friend. A Collection 
of Receipts and Practical Suggestions relating to Aquaria, Bronzing, 
Cements, Drawing, Dyes, Electricity, Gilding, Glass-working, Glues, 
Horology, Lacquers, Locomotives, Magnetism, Metal-working, Mod- 
elling, Photography, Pyrotechny, Railways, Solders, Steam-Engine, 
Telegraphy, Taxidermy, Varnishes, Waterproofing, and Miscellane- 
ous Tools^ Instruments, Machines, and Processes connected with 
the Chemical and Mechanic Arts. With numerous diagrams and 
woodcuts. Fancy cloth $1.50 

BACON, F. W. A Treatise on the Richards Steam- 
Engine Indicator, with directions for its use. By Charles T. Porter. 
Revised, with notes and large additions as developed by American 
practice ; with an appendix containing useful formulae and rules for 
engineers. Illustrated. Fourth edition. i2mo, cloth . . . $i.oc 



I). VAN NO ST/? A AW COMPANY'S 



BARBA, J. The Use of Steel for Constructive Purposes. 

Method of Working Applying, and Testing Plates and Bars. With 
a Preface by A. L. Holley, C.E. i2mo, cloth $1.50 

BARRETT, Capt. EDWARD. Dead Reckoning; or, 
Day's Work. 8vo, flexible cloth $r.oo 

BEILSTEIN, F. An Introduction to Qualitative Chem- 
ical Analysis. Translated by I. J. Osbun. i2mo, cloth ....?$ 

BECKWITH, ARTHUR. Pottery. Observations on the 
Materials and Manufacture of Terra-Cotta, Stoneware, Fire-Brick, 
Porcelain, Earthenware, Brick, Majolica, and Encaustic Tiles. 8vo, 
paper 60 

BLAKE, W. P. Report upon the Precious Metals. 

Being Statistical Notices of the principal Gold and Silver producing 
regions of the World, represented at the Paris Universal Exposition. 
8vo, cloth $2.00 

Ceramic Art. A Report on Pottery, Porcelain, Tiles, Terra- 
Cotta, and Brick. 8vo, cloth $2.00 

BLYTH, A. WYNTER, M.R.C.S., F.C.S. Foods: their 

Composition and Analysis. Third edition. Crown 8vo, cloth, $6.00 

— Poisons : their Effects and Detection. Second edition. 
Crown 8vo, cloth $6.00 

BOTTONE, S. R. Electrical Instrument Making for 

Amateurs. A Practical Handbook. With 48 illustrations. i2mo, 

cloth $1.20 

BOW, R. H. A Treatise on Bracing. With its application 
to Bridges and other Structures of Wood or Iron. 156 illustrations. 
8vo, cloth $1.50 

BOWSER, Prof. E. A. An Elementary Treatise on 

Analytic Geometry. Embracing Plain Geometry, and an Intro- 
duction to Geometry of three Dimensions. i2mo, cloth. Tenth 
edition $ l -75 

An Elementary Treatise on the Differential and In- 
tegral Calculus. With numerous examples. i2mo, cloth. Ninth 
edition $ 2 - 2 5 

— -An Elementary Treatise on Analytic Mechanics. 

With numerous examples. i2mo, cloth. Third edition . . $3- 00 

An Elementary Treatise on Hydro -Mechanics. With 

numerous examples. i2mo, cloth. Second edition . . . . $2.50 

— — Academic Algebra $1.5° 

■ College Algebra. $*-<* 



SCIENTIFIC PUBLICATIONS. 



BOWIE, AUG. J,, Jun., M.E. A Practical Treatise on 

Hydraulic Mining in California. With Description of the Use and 
Construction of Ditches, Flumes, Wrought-iron Pipes, and Dams; 
Flow of Water on Heavy Grades, and its Applicability, under High 
Pressure, to Mining. Second edition. Small quarto, cloth. Illus- 
trated $S-oq 

BURGH, N. P. Modern Marine Engineering. Applied 
to Paddle and Screw Propulsion. Consisting of 36 colored plates, 259 
practical woodcut illustrations, and 403 pages of descriptive matter. 
The whole being an exposition of the present practiced James Watt 
& Co., J. & G. Rennie, R. Napier & Sons, and other celebrated 
firms. Thick 4to voU Half morocco $10.00 



BURT, W. A. Key to the Solar Compass, and Survey- 
or's Companion. Comprising all the rules necessary for use in the 
field ; also description of the Linear Surveys and Public Land System 
of the United States, Notes on the Barometer, Suggestions for an 
Outfit for a Survey of Four Months, etc. Fifth edition. Pocket-book 
form, tuck $2.50 

CAIN, Prof. WM. A Practical Treatise on Voussoir 

and Solid and Braced Arches. i6mo," cloth extra .... $1.75 

CALDWELL, Prof. GEO. C, and BRENEMAN, Prof. 

A. A. Manual of Introductory Chemical Practice. For the use oi 
Students in Colleges and Normal and High Schools. Third edition, 
revised and corrected. 8vo, cloth. Illustrated. New and enlarged 
edition $1.50 

CAMPIN, FRANCIS. On the Construction of Iron 

Roofs. A Theoretical and Practical Treatise, with wood-cuts and 
Plates of Roofs recently executed. 8vo, cloth $2.00 

CHURCH, JOHN A. Notes of a Metallurgical Journey 

i \ Europe. 8vo, cloth $2.oc 

CLARK, D. KIN NEAR, C.E. A Manual of Rules, 

Tables, and Data for Mechanical Engineers. Based on the most 
recent investigations. Illustrated with numerous diagrams. 1,012 

p iges. 8vo, cloth. Third edition $500 

Half morocco $7.50 

CLARKE, T. C. Description of the Iron Railway Bridge 

over the Mississippi River at Quincy, 111. Illustrated with 21 litho- 
graphed plans. 4to, cloth $7-5 r 



Z>. VAN NOSTRAND COMPANY'S 



CLEVENGER, S. R. A Treatise on the Method of 

Government Surveying as prescribed by the U. S. Congress and 
Commissioner of the General Land Office, with complete Mathe- 
matical, Astronomical, and Practical Instructions for the use of the 
United States Surveyors in the field. i6mo, morocco . . . $2.50 

COLBURN, ZERAH. The Gas- Works of London, nmo, 
boards 6 

COLLINS, JAS. E. The Private Book of Useful Alloys 

and Memoranda for Goldsmiths, Jewellers, etc. i8mo, cloth . .50 

CORNWALL, Prof. H. B. Manual of Blow-Pipe 

Analysis, Qualitative and Quantitative. With a Complete System of 
Descriptive Mineralogy. 8vo, cloth, with many illustrations, $2.50 

CRAIG, B. F. Weights and Measures. An account of the 
Decimal System, with Tables of Conversion for Commercial and 
Scientific Uses. Square 32mo, limp cloth 50 

CRAIG, Prof. THOS. Elements of the Mathematical 

Theory of Fluid Motion. i6mo, cloth $1.25 

CUMMING, LINNAEUS, M.A. Electricity treated 

Experimentally. For the use of Schools and Students. New edition. 
i2mo, cloth $1.50 

DIXON, D. B. The Machinist's and Steam-Engineer's 

Practical Calculator. A Compilation of Useful Rules, and Problems 
arithmetically solved, together with General Information applicable 
to Shop-Tools, Mill-Gearing, Pulleys and Shafts, Steam-Boilers and 
Engines. Embracing valuable Tables, and Instruction in Screw- 
cutting, Valve and Link Motion, etc. i6mo, full morocco, pocket 
form $2.00 

DODD, GEO. Dictionary of Manufactures, Mining, 

Machinery, and the Industrial Arts. i2mo, cloth . » . . $1.50 

DORR, B. F. The Surveyors Guide and Pocket Table 

Book. i8mo, morocco flaps . . . . $2.00 

DUBOIS, A. J. The New Method of Graphical Statics. 

With 60 illustrations. 8vo, cloth $1.50 

EDDY, Prof. H. T. Researches in Graphical Statics. 

Embracing New Constructions in Graphical Statics, a New General 
Method in Graphical Statics, and the Theory of Internal Stress in 
Graphical Statics. 8vo, cloth * $1-5° 

EMOT, Prof. C. W., and STORER, Prof. F. H. A 

Compendious Manual of Qualitative Chemical Analysis. Revised 
with the co-operation of the authors, by Prof. William R. Nichols. 
Illustrated. i2mo, cloth $1.50 



SCIENTIFIC PUBLICATIONS. 



FANNING, J. T. A Practical Treatise on Hydraulic 
and Water-Supply Engineering. Relating to the Hydrology, Hydro- 
dynamics, and Practical Construction of Water- Works in North 
America. Fifth edition. With numerous tables and 180 illustra- 
tions. 650 pages. 8vo, cloth. Sixth edition, revised, enlarged, and 
new tables and illustrations added $5.00 

FISKE, Lieut. BRADLEY A., U.S.N. Electricity in 

Theory and Practice ; or, The Elements of Electrical Engineering. 
Fifth edition. 8vo, cloth $2.50 

FORBES, Prof. GEORGE. Galvanic Batteries. In Press. 

FOSTER, Gen. J. G., U.S.A. Submarine Blasting in 
Boston Harbor, Massachusetts. Removal of Tower and Corwin 
Rocks. Illustrated with 7 plates. 4to, cloth $3.50 

FRANCIS, JAS. B., C.E. Lowell Hydraulic Experi- 
ments. Being a selection from experiment on Hydraulic Motors, 
on the Flow of Water over Weirs, in open Canals of uniform rec- 
tangular section, and through submerged Orifices and diverging 
Tubes. Made at Lowell, Mass. Fourth edition, revised and en- 
larged, with many new experiments, and illustrated with 23 copper- 
plate engravings. 4to, cloth $15.00 

GILLMORE, Gen. Q. A. Treatise on Limes, Hydraulic 

Cements, and Mortars. Papers on Practical Engineering, United 
States Engineer Department, No. 9, containing Reports of numerous 
Experiments conducted in New York City during the years 1858 to 
1 86 1, inclusive. With numerous illustrations. 8vo, cloth . $4.00 

Practical Treatise on the Construction of Roads, 

Streets, and Pavements. With 70 illustrations. i2mo, cloth, $2.00 

Report on Strength of the Building-Stones in the 

United States^ etc. 8vo, illustrated, cloth $1.00 

GOODEVE, T. M. A Text-Book on the Steam-Engine. 

With a supplement on Gas-Engines. Ninth edition. 143 illustra- 
tions. i2mo, cloth $2.00 

GORDON, J. E. H. Four Lectures on Static Induction. 
i2mo, cloth $0.80 

— School Electricity, nmo, cloth $2.00 

GRIMSHAW, ROBERT, M.E. The Steam Boiler 

Catechism. A Practical Book for Steam Engineers, Firemen, and 
Owners and Makers of Boilers of any kind. Illustrated. Thick 
i8mo, cloth $2.00 

GRUNER, M. L. The Manufacture of Steel. Translated 
from the French, by Lenox Smith; with an appendix on the Bessemer 
process in the United States, by the translator. Illustrated. 8vo, 
cloth , . . $3.59 



D. VAN NO STRAND COMPANY'S 



HALF-HOURS WITH MODERN SCIENTISTS. 

Lectures and Essays, by Profs. Huxley, Barker, Stirling, Cope, 
Tyndall, Wallace, Roscoe, Huggins, Lockyer, Young, Mayer, and 
Reed. Being the University Series bound up. With a general in- 
troduction by Noah Porter, President of Yale College. 2 vols,, 
i2mo, cloth, illustrated $2.50 

HAMILTON, W. G. Useful Information for Railway 

Men. Sixth edition, revised and enlarged. 562 pages, pocket form. 
Morocco, gilt $2.00 

HARRISON, W. ^ The Mechanic's Tool Book. With 
Practical px \Lcs ana Suggestions for use of Machinists, Iron- Workers, 
s^ Others. Illustrated with 44 engravings. i2mo, cloth. . $1.50 

riASKINS, C. H. The Galvanometer and its Uses. A 

Manual for Electricians and Students. Second edition. i2mo, 
morocco $1.50 

HEAP, Major D. P., U.S.A. Electrical Appliances of 

the Present Day. Report uf the Paris Electrical Exposition of 1881. 
250 illustrations. 8vo, cloth $2.00 

HERRMANN, Gustav. The Graphical Statics of Mech- 
anism. A Guide for the Use of Machinists, Architects, and 
Engineers; and also a Text-book for Technical Schools. Trans- 
lated and annotated by A. P. Smith, M.E. i2mo, cloth, 7 folding 
plates $2.00 

HEWSON, WM. Principles and Practice of embanking 

Lands from River Floods, as applied to the Levees of the Missis- 
sippi. 8vo, cloth $2.00 

HENRICI, OLANE. Skeleton Structures, Applied to 

the Building of Steel and Iron Bridges. Illustrated . . . $1.50 

HOLLEY, ALEXANDER L. Railway Practice. Ameri- 
can and European Railway Practice in the Economical Generation of 
Steam, including the Materials and Construction of Coal-burning 
Boilers, Combustion, the Variable Blast, Valorization, Circulation, 
Superheating, supplying and heating Feed Wnter, etc., and the Adap- 
tation of Wood and Coke-burning Engines to Coal-burning; and in 
Permanent Way, including Road-bed, Sleeper*, Rails, Joint Fasten- 
ings, Street Railways, etc. With 77 lithographed plates. Folio, 
cloth $12.00 

HOWARD, C. R. Earthwork Mensuration on the Basis 
of the Prismoidal Formulae. Containing Simple and Labor-saving 
Method of obtaining Prismoidal Contents directly from End Areas. 
Illustrated by Examples, and accompanied by Pkin Rules for Prac- 
tical Uses. Illustrated. 8vo, cloth $1-5° 

ISHERWOOD, B. F. Engineering Precedents £*r Steam 

Machinery. Arranged in the most practical and iwM manner for 
Engineers. With illustrations. 2 vols, in 1. 8vo, doth . . $2.50 



SCIENTIFIC PUBLICATIONS. 



JANNETTAZ, EDWARD. A Guide to the Determina- 
tion of Rocks : being an Introduction to Lithology. Translated 
from the French by G. W. Plympton, Professor of Physical Science 
at Brooklyn Polytechnic Institute. i2mo, cloth $1.50 

JONES, H. CHAPMAN. Text-Book of Experimental 

Organic Chemistry for Students. i8mo, cloth $1.00 

JOYNSON, F. H. The Metals used in Construction: 

Iron, Steel, Bessemer Metal, etc. Illustrated. i2mo, cloth . .7s 

— Designing and Construction of Machine Gearing. 
Illustrated. 8vo, cloth $2.00 

KANSAS CITY BRIDGE, THE. With an Account of the 
Regimen of the Missouri River, and a Description of the Methods 
used for Founding in that River. By O. Chanute, Chief Engineer, 
and George Morrison, Assistant Engineer. Illustrated with 5 litho- 
graphic views and 12 plates of plans. 4to, cloth $6.00 

KAPP, GISBERT, C.E. Electric Transmission of 

Energy, and its Transformation, Subdivision, and Distribution. A 
practical handbook. i2mo, cloth $3.00 

KING, W. H. Lessons and Practical Notes on Steam. 

The Steam-Engine, Propellers, etc., for Young Marine Engineers, 
Students, and others. Revised by Chief Engineer J. W. King, United 
States Navy. Nineteenth edition, enlarged. 8vo, cloth . . $2.00 

KIRKWOOD, JAS. P. Report on the Filtration of 

River Waters for the supply of Cities, as practised in Europe, made 
to the Board of Water Commissioners of the city of St. Louis. 
Illustrated by 30 double-plate engravings. 4to, cloth . . . $15.00 

LARRABEE, C. S. Cipher and Secret Letter and Tele- 
graphic Code, with Hogg's Improvements. The most perfect Secret 
Code ever invented or discovered. Impossible to read without the 
key. i8mo, cloth 60 

LARDEN, W., M«A. A School Course on Heat. 121110, 

half leather $2.00 

LEITZE, ERNST. Modern Heliographic Processes. 

A Manual of Instruction in the Art of Reproducing Drawings, 
Engravings, etc., by the action of Light. With 32 wood- cuts and 
ten specimens of Heliograms. 8vo, cloth $3.00 

LOCKWOOD, THOS. D. Electricity, Magnetism, and 

Electro-Telegraphy. A Practical Guide for Students, Operators, and 
Inspectors. 8vo, cloth $2.50 

LORING, A. E. A Handbook on the Electro-Magnetic 

Telegraph. Paper boards co 

Cloth 75 

Morocco , $1.00 



D. VAN NO STRAND COMPANY'S 



MAIER, JULIUS, Ph.D. Arc and Glow Lumps- A 

Practical Handbook on Electric Lighting. Illustrated. lsmo, 
cloth $3.00 

MACGREGOR, WM. Gas-Engines : their Theory and 

Management. Folding plates, i2mo, cloth $3.00 

MACCORD, Prof. C. W. A Practical Treatise on the 

Slide- Valve by Eccentrics, examining by methods the action of the 
Eccentric upon the Slide-Valve, and explaining the practical pro 
cesses of laying out the movements, adapting the Valve for its 
various duties in the Steam-Engine. Second edition. Illustrated. 
4to, cloth $2.50 

MCCULLOCH, Prof. R. S. Elementary Treatise on 

the Mechanical Theory of Heat, and its application to Air and 
Steam Engines. 8vo, cloth $3.50 

MERRILL, Col. WM. E., U.S.A. Iron Truss Bridges 

for Railroads. The method of calculating strains in Trusses, with a 
careful comparison of the niost prominent Trusses, in reference to 
economy in combination, etc. Illustrated. 4to, cloth. 4th ed., $5.00 

MICHIE, Prof. P. S. Elements of Wave Motion relat- 
ing to Sound and Light. Second edition. Textbook for the United 
States Military Academy. 8vo, cloth, illustrated #5.00 

MINIFIE, WM. Mechanical Drawing. A Textbook of 
Geometrical Drawing for the use of Mechanics and Schools, in 
which the Definitions and Rules of Geometry are familiarly explained; 
the Practical Problems are arranged from the most simple to the 
more complex, and in their description technicalities are avoided as 
much as possible. With illustrations for Drawing Plans, Sections, 
and Elevations of Railways and Machinery; an Introduction to 
Isometrical Drawing, and an Essay on Linear Perspective and 
Shadows. Illustrated with over 200 diagrams engraved on steel. 
Ninth thousand. With an appendix on the Theory and Application 
of Colors. 8vo, cloth $4.00 

Geometrical Drawing. Abridged from the octavo edition, 

for the use of schools. Illustrated with 48 steel plates. Eighth 
edition. i2mo, cloth $2.00 

MODERN METEOROLOGY. A Series of Six Lectures, 
delivered under the auspices of the Meteorological Society in 1878. 
Illustrated. i2mo, cloth $1-5° 

MORRIS, E. Easy Rules for the Measurement of 

Earthworks by means of the Prismoidal Formula. 8vo, cloth, 
illustrated $1.50 

MOTT, H. A., Jun. A Practical Treatise on Chemistry 

(Qualitative and Quantitative Analysis), Stoichiometry, Blow-pipe 
Analysis, Mineralogy, Assaying, Pharmaceutical Preparations, Human 
Secretions, Specific Gravities, Weights and Measures, etc. New 
edition, 1883. 650 pages. 8vo, cloth $4.00 



SCIENTIFIC PUBLICATIONS. 



MULLIN, JOSEPH P., M.E. Modern Moulding and 

Pattern- Making. A Practical Treatise upon Pattern-Shop and 
Foundry Work : embracing the Moulding of Pulleys, Spur Gears, 
Worm Gears, Balance-Wheels, Stationary Engine and Locomotive 
Cylinders, Globe Valves, Tool Work, Mining Machinery, Screw Pro- 
pellers, Pattern-Shop Machinery, and the latest improvements in 
English and American Cupolas ; together with a large collection of 
original and carefully selected Rules and Tables, for every-day use 
in the Drawing-Office, Pattern-Shop, and Foundry. 121110, cloth, 
illustrated $2.50 

MUNRO, JOHN, C.E., and JAMIESON, ANDREW, 

C.E. A Pocketbook of Electrical Rules and Tables, for the use of 
Electricians and Engineers. Fifth edition, revised and enlarged. 
With numerous diagrams. Pocket size. Leather .... $2.50 

NAQUET, A. Legal Chemistry. A Guide to the Detection 
of Poisons, Falsification of Writings, Adulteration of Alimentary and 
Pharmaceutical Substances, Analysis of Ashes, and examination of 
Hair, Coins, Arms, and Stains, as applied to Chemical Jurisprudence, 
for the use of Chemists, Physicians, Lawyers, Pharmacists, and 
Experts. Translated, with additions, including a list of books and 
memoirs on Toxicology, etc., from the French, by J. P. Battershall, 
Ph.D., with a preface by C. F. Chandler, Ph.D., M.D., LL.D. 121110, 
cloth $2.00 

NOBLE, W. H. Useful Tables. Pocket form, cloth, .50 

NIPHER, FRANCIS E., A.M. Theory of Magnetic 

Measurements, with an appendix on the Method of Least Squares. 
i2mo, cloth $1.00 

NUGENT, E. Treatise or Optics; or, Light and Sight, 

theoretically and practically treated, with the application to Fine Art 
and Industrial Pursuits. With 103 illustrations. i2mo, cloth, $1.50 

PEIRCE, B. System of Analytic Mechanics. 4to, 
cloth . . . . , $ 1 0.0c 

PLANE TABLE, The. Its Uses in Topographical Surveying. 
From the Papers of the United States Coast Survey. Illustrated. 
8vo, cloth $2.00 

" This work gives a description of the Plane Table employed at the 
United States Coast Survey office, and the manner of using it." 

PLATTNER. Manual of Qualitative and Quantitative 

Analysis with the Blow-Pipe. From the last German edition, revised 
and enlarged, by Prof. Th. Richter of the Royal Saxon Mining 
Academy. Translated by Prof. H. B. Cornwall, assisted by John H. 
Caswell. Illustrated with Sy woodcuts and one lithographic plate 
Fourth edition, revised. 560 pages. 8vo, cloth $5.00 



D. VAN NO STRAND COMPANY'S 



PLANTE, GASTON. The Storage of Electrical Energy, 

and Researches in the Effects created by Currents, combining Quan- 
tity with High Tension. Translated from the French by Paul B. 
Elwell. 89 illustrations. 8vo $4.00 

PLYMPTON, Prof. GEO. W. The Blow-Pipe. A 

Guide to its use in the Determination of Salts and Minerals. Com< 
piled from various sources. i2mo, cloth $1.50 

-—The Aneroid Barometer: its Construction and Use. 

Compiled from several sources. i6mo, boards, illustrated . .50 
Morocco $1.00 

The Star-Finder ; or, Planisphere, with Movable 



Horizon. Printed in colors on fine cardboard, and in accordance 
with Proctor's Star Atlas 50 

POCKET LOGARITHMS, to Four Places of Decimals, 

including Logarithms of Numbers, and Logarithmic Sines and Tan- 
gents to Single Minutes. To which is added a Table of Natural 
Sines, Tangents, and Co-Ta'ngents. i6mo, boards .... .50 
Morocco $1.00 

POOK, S. M. Method of comparing the Lines and 

Draughting Vessels propelled by Sail or Steam. Including a chapter 
on Laying-off on the Mould-Loft Floor. 1 vol. 8vo, with illustra- 
tions, cloth $5.00 

POOLE, Capt. D. C. Among the Sioux of Dakota; or, 

Eighteen Months' Experience as an Indian Agent. 121110 . $1.25 

POPE, F. L. Modern Practice of the Electric Tele- 
graph. A Handbook for Electricians and Operators. Eleventh 
edition, revised and enlarged, and fully illustrated. 8vo, cloth, $1.50 

PREECE, W. H., and MAIER, J. The Telephone. In 

Press. 

PRESCOTT, Prof. A. B. Organic Analysis. A Manual 
of the Descriptive and Analytical Chemistry of certain Carbon Com- 
pounds in Common Use; a Guide in the Qualitative and Quantitative 
Analysis of Organic Materials in Commercial and Pharmaceutical 
Assays, in the estimation of Impurities under Authorized Standards, 
and in Forensic Examinations for Poisons, with Directions for Ele- 
mentary Organic Analysis. 8vo, cloth $5.00 

— — Outlines of Proximate Organic Analysis, for the 

Identification, Separation, and Quantitative Determination of the 
more commonly occurring Organic Compounds. i2mo, cloth, $1.75 

• Chemical Examination of Alcoholic Liquors. A 

Manual of the Constituents of the Distilled Spirits and Fermented 
Liquors of Commerce, and their Qualitative and Quantitative Deter- 
minations. 121110, cloth $1.50 



SCIENTIFIC PUBLICATIONS. 



PRESCOTT, Prof. A. B. First Book in Qualitative 
Chemistry. Second edition. 121110, cloth . . . . . . . $1.50 

and OTIS COE JOHNSON. Qualitative Chemical 

Analysis. A Guide in the Practical Study of Chemistry and in 
the work of Analysis. Fourth fully revised edition. With De- 
scriptive Chemistry extended throughout $3-50 

PULSIFER, W. H. Notes for a History of Lead. 8vo 3 

cloth, gilt tops $4.00 

PYNCHON, Prof. T. R. Introduction to Chemical 

Physics, designed for the use of Academies, Colleges, and High 
Schools. Illustrated with numerous engravings, and containing 
copious experiments with directions for preparing them. New 
edition, revised and enlarged, and illustrated by 269 illustrations on 
wood. Crown 8vo, cloth $3-oo 

RAMMELSBERG, C. F. Guide to a Course of Quan- 
titative Chemical Analysis, especially of Minerals and Furnace Pro- 
ducts. Illustrated by examples. Translated by J. Towler, M.D. 
8vo, cloth $2.25 

RANDALL, P. M. Quartz Operator's Handbook. New 

edition, revised and enlarged, fully illustrated. 121110, cloth . $2.oc 

RANKINE, W. J. MACQUORN, C.E., LL.D., F.R.S. 

Applied Mechanics. Comprising the Principles of Statics and Cine- 
matics, and Theory of Structures, Mechanism, and Machines. With 
numerous diagrams. Eleventh edition. Crown 8vo, cloth . $5.00 

■ Civil Engineering. Comprising Engineering Surveys, Earth- 
work, Foundations, Masonry, Carpentry, Metal- Work, Roads, Rail- 
ways, Canals, Rivers, Water- Works, Harbors, etc. With numerous 
tables and illustrations. Sixteenth edition. Crown 8vo, cloth, $6.50 

■ Machinery and Millwork. Comprising the Geometry, 

Motions, W r ork, Strength, Construction, and Objects of Machines, 
etc. Illustrated with nearly 300 woodcuts. Sixth edition. Crown 
8vo, cloth $5.00 

The Steam -Engine and Other Prime Movers. With 



diagram of the Mechanical Properties of Steam, folding plates, 
numerous tables and illustrations. Twelfth edition. Crown 8vo, 
cloth $5.00 

- Useful Rules and Tables for Engineers and Others. 
With appendix, tables, tests, and formulae for the use of Electrical 
Engineers. Comprising Submarine Electrical Engineering, Electric 
Lighting, and Transmission of Power. By Andrew Jamieson, C.E., 
F.R.S. E. Sixth edition. Crown 8vo, cloth $4.00 

- A Mechanical Textbook. By Prof. Macquorn Rankine 
and E. F. Bamber, C.E. With numerous illustrations. Third 
edition $3.50 



D. VAN NO STRAND COMPANY'S 



REED'S ENGINEERS' HANDBOOK, to the Local 

Marine Board Examinations for Certificates of Competency as First 
and Second Class Engineers. By W. H. Thorn. With the answers 
to the Elementary Questions. Illustrated by 297 diagrams and 36 
large plates. Twelfth edition, revised and enlarged. 8vo, cloth, $4.50 

REID, Lieut.-Col. W. Law of Storms. An attempt to 
develop the Law of Storms by means of Facts, arranged according 
to Place and Time, and hence to point out a Cause for the Variable 
Winds, with a View to Practical Use in Navigation. Large 8vo, 
cloth, with maps $5.00 

RICE, Prof. J. M., and JOHNSON, Prof. W. W. On a 

New Method of obtaining the Differentials of Functions, with espe 
cial reference to the Newtonian Conception of Rates or Velocities, 
i2mo, paper 5c 

ROEBLING, J. A. Long and Short Span Railway 

Bridges. Illustrated with large copperplate engravings of plans and 
views. Imperial folio, cloth $25.00 

ROGERS, Prof. H. D. The Geology of Pennsylvania. 

A Government Survey, with a General View of the Geology of the 
United States, essays on the Coal Formation and its Fossils, and a 
description of the Coal Fields of North America and Great Britain. 
Illustrated with plates and engravings in the text. 3 vols. 4to, 
cloth, with portfolio of maps $15.00 

ROSE, JOSHUA, M.F. The Pattern-Maker's Assistant. 

Embracing Lathe Work, Branch Work, Core Work, Sweep Work, 
and Practical Gear Constructions, the Preparation and Use of Tools, 
together with a large collection of useful and valuable Tables. Third 
edition. Illustrated with 250 engravings. 8vo, cloth . . . $2.50 

SABINE, ROBERT. History and Progress of the 

Electric Telegraph. With descriptions of some of the apparatus. 
Second edition, with additions. i2mo, cloth $1.25 

SAELTZER, ALEX. Treatise on Acoustics in Connec- 
tion with Ventilation. i2mo, cloth $1.00 

SALOMONS, Sir DAVID, M.A. Management of 

Accumulators and Private Electric-Light Installations. A Practical 
Handbook. Third edition, revised and enlarged. i2mo, cloth, $1.20 

SAUNNIER, CLAUDIUS. Watchmaker's Handbook. 

A Workshop Companion for those engaged in Watchmaking and 
allied Mechanical Arts. Translated by J. Tripplin and E. Rigg. 
Second edition, revised and appendix. i2mo, cloth .... $3.50 

SAWYER, W. E. Electric-Lighting by Incandescence, 

and its Application to Interior Illumination. A Practical Treatise. 
With 96 illustrations. Third edition. 8vo, cloth 



SCIENTIFIC PUBLICATIONS. 



SCHUMANN, F. A Manual of Heating and Ventilation 

in its Practical Application, for the use of Engineers and Architects. 
Embracing a series of Tables and Formulae for dimensions of heat- 
ing, flow and return pipes for steam and hot-water boilers, flues, etc. 
i2mo, illustrated, full roan . . . $1.50 

— — Formulas and Tables for Architects and Engineers 

in calculating the strains and capacity of structures in Iron and 
Wood. i2mo, morocco, tucks $1.50 

SCIENCE SERIES, Van Nostrand's. See List. 

SCRIBNER, J. M. Engineers' and Mechanics' Com- 

panion. Comprising United States Weights and Measures, Men- 
suration of Superfices and Solids, Tables of Squares and Cubes, 
Square and Cube Roots, Circumference and Areas of Circles, the 
Mechanical Powers, Centres of Gravity, Gravitation of Bodies, Pen- 
dulums, Specific Gravity of Bodies, Strength, Weight, and Crush of 
Materials, Water- Wheels, Hydrostatics, Hydraulics, Statics, Centres 
of Percussion and Gyration, Friction Heat, Tables of the Weight of 
Metals, Scantling, etc., Steam and the Steam-Engine. Nineteenth 
edition, revised. i6mo, full morocco $1.5(1 

. Engineers', Contractors', and Surveyors' Pocket 

Table-Book. Comprising Logarithms of Numbers, Logarithmic 
Sines and Tangents, Natural Sines and Natural Tangents, the 
Traverse Table, and a full and complete set of Excavation and Em- 
bankment Tables, together with numerous other valuable tables for 
Engineers, etc. Eleventh edition, revised. i6mo, full morocco, $2. o« 

SCHELLEN, Dr. H. Magneto-Electric and Dynamo- 
Electric Machines : their Construction and Practical Application to 
Electric Lighting, and the Transmission of Power. Translated from 
the third German edition by N. S. Keith and Percy Neymann, Ph.D. 
With very large additions and notes relating to American Machines, 
by N. S. Keith. Vol. I., with 353 illustrations. Second edi- 
tion $5-oc 

SHIELDS, J. E. Notes on Engineering Construction. 

Embracing Discussions of the Principles involved, and Descriptions 
of the Material employed, in Tunnelling, Bridging, Canal and Road 
Building, etc. i2mo, cloth $i-5c 

SHOCK, Chief-Eng. W. H. Steam-Boilers : their De- 
sign, Construction, and Management. 450 pages text. Illustrated 
with 150 woodcuts and 36 full-page plates (several double). Quarto, 
half morocco 

SHREVE, S. H. A Treatise on the Strength of Bridges 

and Roofs. Comprising the determination of Algebraic formulas for 
strains in Horizontal, Inclined or Rafter, Triangular, Bowstring, 
Lenticular, and other Trusses, from fixed and moving loads, with 
practical applications and examples, for the use of Students and En- 
gineers. 87 woodcut illustrations. Third edition. 8vo, cloth, $3.50 



D. VAN NO STRAND COMPANY'S 



SHUNK, W. F. The Field Engineer. A handy book ol 
practice in the Survey, Location, and Track-work of Railroads, con- 
taining a large collection of Rules and Tables, original and selected, 
applicable to both the Standard and Narrow Gauge, and prepared 
with special reference to the wants of the young Engineer, Seventh 
edition. i2mo, morocco, tucks $2.50 

SIMMS, F. W. A Treatise on the Principles and Prac- 
tice of Levelling. Showing its application to purposes of Railway 
Engineering, and the Construction of Roads, etc. Revised and 
corrected, with the addition of Mr. Laws' Practical Examples for 
setting out Railway Curves. Illustrated. 8vo, cloth . . . $2.50 

SLATER, J. W. Sewage Treatment, Purification, and 

Utilization. A Practical Manual for the Use of Coporations, Local 
Boards, Medical Officers of Health, Inspectors of Nuisances, Chem- 
ists, Manufacturers, Riparian Owners, Engineers, and Rate-payers. 
i2mo, cloth $2.25 

SMITH, ISAAC W., C.E. The Theory of Deflections 

and of Latitudes and Departures. With special applications to 
Curvilinear Surveys, for Alignments of Railway Tracks. Illustrated. 
i6mo, morocco, tucks . . , $3-oo 

SIMMS, FRED. W. Practical Tunnelling. Explaining 

in detail Setting-out of the Work, Shaft-sinking, Sub-excavating, 
Timbering, etc., with cost of work. 8vo, cloth . . . . $7.50 

STAHL, A. W., and WOODS, A. T. Elementary 

Mechanism. A Text-Book for Students of Mechanical Engineering 
i2ino . $2.00 

STALEY, CADY, and PIERSON, GEO. S. The Sepa- 
rate Svstem of Sewerage- its Theory and Construction. 8vo, 
cloth ' $ 2 -5o 

STEVENSON, DAVID, F.R.S.E. The Principles and 

Practice of Canal and River Engineering. Revised by his sons 
David Alan Stevenson, B. Sc., F.R.S.E., and Charles Alexander 
Stevenson, B. Sc, F.R.S.E., Civil Engineer. Third edition, with 
17 plates. 8vo, cloth $10.00 

The Design and Construction of Harbors. A Treatise 

on Maritime Engineering. Third edition, with 24 plates. 8vo, 
cloth $io-°° 

STILES, AMOS. Tables for Field Engineers. De- 
signed for use in the field. Tables containing all the functions of a 
one degree curve, from which a corresponding one can be found for 
any required degree. Also, Tables of Natural Sines and Tangents. 
i2mo, morocco, tucks $2.00 

STILLMAN, PAUL. Steam-Engine Indicator and the 

Improved Manometer Steam and Vacuum Gauges: their Utility and 
Application. New edition. i2mo, flexible cloth $i.o« 



SCIENTIFIC PUBIJCA TIONS. 



STONEY, B. D. The Theory of Stresses in Girders 

and Similar Structures. With observations on the application o£ 
Theory to Practice, and Tables of Strength, and other properties ol 
Materials. New revised edition, with numerous additions on Graphic 
Statics, Pillars, Steel, Wind Pressure, Oscillating Stresses, Working 
Loads, Riveting, Strength and Tests of Materials. 8vo, yyy pages, 
143 illustrations, and 5 folding plates $12.50 

STUART, B. How to become a Successful Engineer. 

Being Hints to Youths intending to adopt the Profession. Sixth 
edition. i2mo, boards 50 

SWEET, S. H. Special Report on Coal, showing its 

Distribution, Classification, and Cost delivered over different routes 
to various points in the State of New York and the principal cities 
on the Atlantic Coast. With maps. 8vo, cloth $3.00 

SWINTON, ALAN A. CAMPBELL. The Elementary 

Principle of Electric Lighting. Illustrated. i2mo, cloth. . . .60 

TONER, J. M. Dictionary of Elevations and Climatic 

Register of the United States. Containing, in addition to Eleva- 
tions, the Latitude, Mean Annual Temperature, and the total Annual 
Rainfall of many localities, With a brief Introduction on the 
Orographic and Physical Peculiarities of North America. 8vo, 
cloth ' $3.75 

TUCKER, Dr. J. H. A Manual of Sugar Analysis. In- 
cluding the Applications in General of Analytical Methods to the 
Sugar Industry. With an Introduction on the Chemistry of Cane 
Sugar, Dextrose, Levulose, and Milk Sugar. 8vo, cloth, illus- 
trated S3. 50 

TUNNER, P. A Treatise on Roll-Turning for the 

Manufacture of Iron. Translated and adapted by John B. Pearse of 
the Pennsylvania Steel- Works, with numerous engravings, woodcuts, 
and folio atlas of plates $10.00 

UNIVERSAL (The) TELEGRAPH CIPHER CODE. 

Arranged for General Correspondence. 121110, cloth . . . Sr.oo 

VAN NOSTRAND'S Engineering Magazine. Complete 
sets, 1869 t0 J 886 inclusive, in 35 vols, in numbers .... S20.00 

Complete sets, in 35 vols., in cloth $40.00 

Complete sets, in 35 vols., in half morocco £90.00 

VAN WAGENEN, T. F. Manual of Hydraulic Mining, 

For the Use of the Practical Miner. i8mo, cloth . . . . $1.00 

WAINWRIGHT, Col. WM. P. Animal Locomotion. 

Radical Mechanics of Animal Locomotion, with Remarks on the 
Setting-up of Soldiers, Horse and Foci, and on the suppling of 
Cavalry Horses. i2mo . .. . . Si. 75 



D. VAN NO STRAND COMPANY. 



i 



WALKER, FRED. W.,M.E. Practical Dynamo-Build- 
ing for Amateurs. i2mo, cloth . . .80 

WALKER, W. H. Screw Propulsion. Notes on Screw 
Propulsion, its Rise and History. 8vo, cloth . . 75 

WANKLYN, J. A. A Practical Treatise on the Exami- 
nation of Milk and its Derivatives, Cream, Butter, and Cheese. 
i2mo, cloth $1.00 

WARD, J. H. Steam for the Million. A Popular Treatise 
on Steam, and its application to the Useful Arts, especially to Navi- 
gation. 8vo, cloth a $1.00 

WARING, GEO. E., Jr. Sewerage and Land Drainage. 

Large Quarto Volume. Illustrated with wood-cuts in the text, and 
full-page and folding plates $6.00 

WATT, ALEXANDER. Electro-Deposition. A Practi- 
cal Treatise on the Electrolysis of Gold, Silver, Copper, Nickel, and 
other Metals, with Descriptions of Voltaic Batteries, Magneto and 
Dynamo-Electric Machines, Thermopiles, and of the Materials 
and Processes used in every Department of the Art, and several chap- 
ters on Electro-Metallurgy. With numerous illustrations. Second 
edition, revised and corrected. Crown 8vo, 568 pages . » . $3.50 

Electro- Metallurgy Practically Treated. Sixth edition, 

considerably enlarged. l2mo, cloth $1.00 

WEISBACH, JULIUS. A Manual of Theoretical 

Mechanics. Translated from the fourth augmented and improved 
German edition, with an Introduction to the Calculus by Eckley B. 
Coxe, A.M., Mining Engineer. 1,100 pages, and 902 woodcut illus- 
trations. 8vo, cloth $10.00 

Sheep $11.00 

WEYRAUCH, J. J. Strength and Calculations of 

Dimensions of Iron and Steel Construction, with reference to the 
Latest Experiments. i2mo, cloth, plates $1.00 

WHIPPLE, S., C.E. An Elementary and Practical 

Treatise on Bridge Building. 8vo, cloth $4.00 

WILLIAMSON, R. S. On the Use of the Barometer on 

Surveys and Reconnoissances. Part I. Meteorology in its Connec- 
tion with Hypsometry. Part II. Barometric Hypsometry. With 
illustrative tables and engravings. 4to, cloth $15.00 

Practical Tables in Meteorology and Hypsometry, 

in connection with the use of the Barometer. 4to, cloth . . $2.50 

WRIGHT, T. W. A Treatise on the Adjustment of 

Observations. With applications to Geodetic Work, and other 
Measures of Precision. 8vo, cloth $4.00 



